scripts: gcc-wrapper: Allow warnings from 3.10.28

Linux-stable v 3.10.28 contains the following forbidden warning when
compiling for 64-bit architectures. Once the remote corrects this warning,
this change should be removed.

arch/arm64/include/asm/cmpxchg.h:162:3: warning: value computed is not used

Change-Id: Ia1c530a9821ee69623950b43a6a7fe130cbaaa04
Signed-off-by: Ian Maund <imaund@codeaurora.org>