Delete IPixelStats HAL

This HAL is no longer necessary since we implemented a generic
vendor-atom interface in the IStats HAL, and migrated all of the current
IPixelStats references to IStats references.

Bug: 122904980
Test: build succeeds
Change-Id: I5e081846135347ef799a3d1662d0680bc28af430
Signed-off-by: Maggie White <maggiewhite@google.com>
17 files changed