omxil: Use the role names video_decoder.wmv1/2

The role name without a suffix, "video_decoder.wmv", is only for
vc1/wmv3/9 (on Samsung Galaxy S III at least). Since certain roles
are substrings of others, require the full string to match when looking
for suitable codecs instead of using strncmp.

Signed-off-by: Martin Storsjö <martin@martin.st>
Revert "omxil: Set the WMV type"

This reverts commit c73e88ce9a79f1b76e7e6a9ec1cf5781555994a5.

The WMV1/2 decoders use a different role name, and this parameter
is unsupported on them. Therefore, there's not much use in trying to
set it at all.

Signed-off-by: Martin Storsjö <martin@martin.st>
omxil: Only try to enable the samsung-specific 420p mode on video decoders

It doesn't make any sense for audio decoders and only leads to
extra log warnings.

Signed-off-by: Martin Storsjö <martin@martin.st>