vmx: adjust macros when loading vectors on ppc64le

vmx: adjust macros when loading vectors on ppc64le

Replaced usage of vec_lvsl to direct unaligned assignment
operation (=). That is because, according to Power ABI Specification,
the usage of lvsl is deprecated on ppc64le.

Changed COMPUTE_SHIFT_{MASK,MASKS,MASKC} macro usage to no-op for powerpc
little endian since unaligned access is supported on ppc64le.

v2:

- replace _LITTLE_ENDIAN with WORDS_BIGENDIAN for consistency
- fixed whitespaces and indentation issues

Signed-off-by: Fernando Seiti Furusato <ferseiti@linux.vnet.ibm.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>