docs: powerpc: fix some issues at vas-api.rst

docs: powerpc: fix some issues at vas-api.rst

There are a few issues on this document, when built via the
building with ``make htmldocs``:

    Documentation/powerpc/vas-api.rst:116: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:116: WARNING: Inline emphasis start-string without end-string.
    Documentation/powerpc/vas-api.rst:117: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:117: WARNING: Inline emphasis start-string without end-string.
    Documentation/powerpc/vas-api.rst:120: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:124: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:133: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:135: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:150: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:151: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:161: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:176: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:253: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:253: WARNING: Inline emphasis start-string without end-string.
    Documentation/powerpc/vas-api.rst:259: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:261: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:266: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:267: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:270: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:271: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:273: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:274: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:277: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:278: WARNING: Definition list ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:280: WARNING: Unexpected indentation.
    Documentation/powerpc/vas-api.rst:287: WARNING: Block quote ends without a blank line; unexpected unindent.
    Documentation/powerpc/vas-api.rst:289: WARNING: Block quote ends without a blank line; unexpected unindent.

Fixes: c12e38b1d52e ("Documentation/powerpc: VAS API")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/fc1138e563bc3a41a9e59b5dd1fe2f6a4bfad253.1592895969.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>