builddeb: fix missing headers in linux-headers package

The kernel headers package (linux-headers) doesn't include several
header files required to build out-of-tree modules.

It makes the package unusable on e.g. ARM architecture:
 /usr/src/linux-headers-3.14.0/arch/arm/include/asm/memory.h:24:25:
 fatal error: mach/memory.h: No such file or directory
 #include <mach/memory.h>
 ^
 compilation terminated.

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Michal Marek <mmarek@suse.cz>