fbdev: arm has __raw I/O accessors, use them in fb.h

This removes the sparse warnings on arm platforms:

warning: cast removes address space of expression
Signed-off-by: Archit Taneja <archit@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: H Hartley Sweeten <hsweeten at visionengravers.com>
Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Russell King <linux@arm.linux.org.uk>

include/linux/fb.h

@@ -553,7 +553,7 @@ static inline struct apertures_struct *alloc_apertures(unsigned int max_num) {
 #define fb_memcpy_fromfb sbus_memcpy_fromio
 #define fb_memcpy_tofb sbus_memcpy_toio
 
-#elif defined(__i386__) || defined(__alpha__) || defined(__x86_64__) || defined(__hppa__) || defined(__sh__) || defined(__powerpc__) || defined(__avr32__) || defined(__bfin__)
+#elif defined(__i386__) || defined(__alpha__) || defined(__x86_64__) || defined(__hppa__) || defined(__sh__) || defined(__powerpc__) || defined(__avr32__) || defined(__bfin__) || defined(__arm__)
 
 #define fb_readb __raw_readb
 #define fb_readw __raw_readw