classes/license: use "1" to set boolean variables

classes/license: use "1" to set boolean variables

The expected usage of COPY_LIC_MANIFEST and COPY_LIC_DIRS appears to be
to set them to "1" to enable; however the test here is just testing
whether they have a value at all, so setting them to "0" would also
enable them which is somewhat disingenuous. Actually check if they are
set to "1" instead in order to fix this.

(From OE-Core rev: 2d8e124adcf27af524eeeae61daf1b21a1c2f27c)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>