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>