Add linux/compiler-gcc5.h to fix builds with gcc5

Add linux/compiler-gcc5/h from the kernel sources at:

commit 5631b8fba640a4ab2f8a954f63a603fa34eda96b
Author: Steven Noonan <steven@uplinklabs.net>
Date:   Sat Oct 25 15:09:42 2014 -0700

    compiler/gcc4+: Remove inaccurate comment about 'asm goto' miscompiles

Signed-off-by: Hans de Goede <hdegoede@redhat.com>