linux-libc-headers: Allow arm kernel headers to coexist on 32/64 bit

linux-libc-headers: Allow arm kernel headers to coexist on 32/64 bit

Its rather sad we need to do this but in order to make combined 32 and 64 bit
SDKs work, we need a common set of headers and this is the delta that
allows things to work. It only applies on arm.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>