Disable macro redefined warnings.

The new kernel headers do:

  #define __bitwise __bitwise__

However, the code redefines __bitwise without undef'ing it first.

This is a temporary fix, b/35721782 filed to fix this.

Change-Id: I6a32d739e7b68236d51e4638478e4eae0f569515
Test: Builds without warningers/errors.