fbdev: do not allow VESA modes without compiled-in drivers

Do not accept VESA modes by the "vga=" kernel parameter if there is no
frame buffer driver compiled-in to handle it.

Also, there is a comment added to the Kconfig description after Werner
Lemberg's suggestion

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=13249Signed-off-by: NKrzysztof Helt <krzysztof.h1@wp.pl>
Reported-by: NWerner Lemberg <wl@gnu.org>
Cc: Michal Januszewski <spock@gentoo.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/Kconfig

@@ -1122,12 +1122,14 @@ config FB_INTEL
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
-	select FB_BOOT_VESA_SUPPORT
+	select FB_BOOT_VESA_SUPPORT if FB_INTEL = y
 	help
 	  This driver supports the on-board graphics built in to the Intel
           830M/845G/852GM/855GM/865G/915G/915GM/945G/945GM/965G/965GM chipsets.
           Say Y if you have and plan to use such a board.
 
+	  To make FB_INTELFB=Y work you need to say AGP_INTEL=y too.
+
 	  To compile this driver as a module, choose M here: the
 	  module will be called intelfb.
 
@@ -1460,7 +1462,7 @@ config FB_SIS
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
-	select FB_BOOT_VESA_SUPPORT
+	select FB_BOOT_VESA_SUPPORT if FB_SIS = y
 	help
 	  This is the frame buffer device driver for the SiS 300, 315, 330
 	  and 340 series as well as XGI V3XT, V5, V8, Z7 graphics chipsets.