Fix shift of the blue component in store_1010102_xr

Bug: https://github.com/flutter/flutter/issues/168849
Change-Id: I43c21535fbea6749f644301e162aacb2bbd5f5c3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/994956
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Jason Simmons <jsimmons@google.com>
(cherry picked from commit bb255dd0252e256a28542475b22711346c319030)
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/999136
Reviewed-by: Heather Miller <hcm@google.com>