Headers should include prototypes they use, otherwise build will
break if we use it without explicitly including io.h:

  CC      arch/powerpc/sysdev/qe_lib/gtm.o
In file included from include/asm/qe.h:20,
                 from arch/powerpc/sysdev/qe_lib/gtm.c:18:
include/asm/immap_qe.h: In function ‘immrbar_virt_to_phys’:
include/asm/immap_qe.h:480: error: implicit declaration of function ‘virt_to_phys’
make[2]: *** [arch/powerpc/sysdev/qe_lib/gtm.o] Error 1
make[1]: *** [arch/powerpc/sysdev/qe_lib] Error 2

gtm.c needs qe.h (which includes immap_qe.h) to use qe_get_brg_clk().
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>