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/arch/i386/Makefile b/arch/i386/Makefile
index bd28f9f..181cc29 100644
--- a/arch/i386/Makefile
+++ b/arch/i386/Makefile
@@ -108,6 +108,7 @@
 # must be linked after kernel/
 drivers-$(CONFIG_OPROFILE)		+= arch/i386/oprofile/
 drivers-$(CONFIG_PM)			+= arch/i386/power/
+drivers-$(CONFIG_FB)                    += arch/i386/video/
 
 CFLAGS += $(mflags-y)
 AFLAGS += $(mflags-y)