drm_hwcomposer: Reorganize modifiers handling logic

Reasons for this change:
1. Remove redundant code lines.
2. Workaround for cases when DRM_FORMAT_MOD_INVALID is set by gralloc.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
1 job for reorganize-modifiers in 43 seconds (queued for 7 seconds)