drm/komeda: Adds internal bpp computing for arm afbc only format YU08 YU10

The drm_format_info doesn't have any cpp or block_size (both are zero)
information for arm only afbc format YU08/YU10. we need to compute it
by ourselves.

Changes since v1:
1. Removed redundant warning check in komeda_get_afbc_format_bpp();
2. Removed a redundant empty line;
3. Rebased the branch.

Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1565073104-24047-1-git-send-email-lowry.li@arm.com
Link: https://patchwork.freedesktop.org/patch/msgid/1565073104-24047-1-git-send-email-lowry.li@arm.com