fbdev: detect primary display device

Add function helper, fb_is_primary_device().  Given struct fb_info, it will
return a nonzero value if the device is the primary display.

Currently, only the i386 is supported where the function checks for the
IORESOURCE_ROM_SHADOW flag.

Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-alpha/fb.h b/include/asm-alpha/fb.h
index ca714a4..fa9bbb9 100644
--- a/include/asm-alpha/fb.h
+++ b/include/asm-alpha/fb.h
@@ -1,7 +1,13 @@
 #ifndef _ASM_FB_H_
 #define _ASM_FB_H_
+#include <linux/device.h>
 
 /* Caching is off in the I/O space quadrant by design.  */
 #define fb_pgprotect(...) do {} while (0)
 
+static inline int fb_is_primary_device(struct fb_info *info)
+{
+	return 0;
+}
+
 #endif /* _ASM_FB_H_ */