mediatek: avoid vertical alignment for FORMAT_BLOB

HAL_PIXEL_FORMAT_BLOB gets resolved into DRM_FORMAT_R8 with height of 1.
Avoid doing any vertical alignment for this case. This format should be
exempt from the 32 vertical alignment requirement from mtk video encoder
in the kernel driver.

BUG=b:270850022
BUG=b:242495495
TEST=test and app work

Change-Id: Ic635c708597b5f5548ad95f34a81943d4cc2c801
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/4364500
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
Commit-Queue: Yiwei Zhang <zzyiwei@chromium.org>
Tested-by: Yiwei Zhang <zzyiwei@chromium.org>