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: Ic16796a599dc577b4fef7f8e2a586162160955fb
Test: Builds without warningers/errors.