Support P010 with Gralloc2 on Gralloc1 passthrough

... by updating the toYCbCrLayout function to more closely follow
the requirements found in the comments of `android_flex_plane_t`.

Bug: b/244411455
Test: untested.
Change-Id: I1173253e25583336bf480160d4f6ac9f72882971
(cherry picked from commit 866abc15)