Use pixel stride of 2 for Y422_I's Y plane

Y422_I's layout is: Y0 Cr0 Y1 Cb0 ...

...which means that successive luminance samples are separated by 2
bytes, not 1.

Bug: 351311764
Test: builds
Flag: EXEMPT bugfix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ff206d6d5d9150bbfeac0dfbe92825d97a7de5b2)
Merged-In: I4c24aae97ef052f6385281dd6e73f748d880decb
Change-Id: I4c24aae97ef052f6385281dd6e73f748d880decb