compiler.h: Do not include sys/io.h on ARM with glibc

<sys/io.h> on ARM hasn't worked for a long, long time, so it was removed
it from glibc upstream.

Remove the include to avoid a compilation failure on ARM with glibc.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Closes: xorg/xserver#840
3 jobs for issue840 in 9 minutes and 33 seconds (queued for 27 minutes and 2 seconds)