x86: Build vga video code only if CONFIG_VIDEO_VGA is defined

When running from coreboot we don't want this code, so make it
optional.

Signed-off-by: Simon Glass <sjg@chromium.org>

README

@@ -1409,6 +1409,13 @@ CBFS (Coreboot Filesystem) support
 		boot.  See the documentation file README.video for a
 		description of this variable.
 
+		CONFIG_VIDEO_VGA
+
+		Enable the VGA video / BIOS for x86. The alternative if you
+		are using coreboot is to use the coreboot frame buffer
+		driver.
+
+
 - Keyboard Support:
 		CONFIG_KEYBOARD
 

arch/x86/lib/Makefile

@@ -32,7 +32,7 @@ COBJS-y	+= realmode.o
 SOBJS-y	+= realmode_switch.o
 
 COBJS-$(CONFIG_SYS_PC_BIOS)	+= bios_setup.o
-COBJS-$(CONFIG_VIDEO)	+= video_bios.o
+COBJS-$(CONFIG_VIDEO_VGA)	+= video_bios.o
 endif
 
 COBJS-y	+= board.o
@@ -50,7 +50,7 @@ COBJS-y	+= relocate.o
 COBJS-y += physmem.o
 COBJS-y	+= string.o
 COBJS-$(CONFIG_SYS_X86_ISR_TIMER)	+= timer.o
-COBJS-$(CONFIG_VIDEO)	+= video.o
+COBJS-$(CONFIG_VIDEO_VGA)	+= video.o
 COBJS-$(CONFIG_CMD_ZBOOT)	+= zimage.o
 
 SRCS	:= $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)