x86: Allow video-BIOS code to be built for SPL

With qemu-x86_64 we need to run the video BIOS while in 32-bit mode, i.e.
SPL. Add a Kconfig option for this, adjust the Makefile rules and use
CONFIG_IS_ENABLED() where needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index b0612ae..90a7618 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -4,16 +4,17 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
 obj-y	+= bdinfo.o
-ifndef CONFIG_X86_64
-ifndef CONFIG_TPL_BUILD
+
+ifndef CONFIG_$(SPL_TPL_)X86_64
 obj-y += bios.o
 obj-y += bios_asm.o
 obj-y += bios_interrupts.o
 endif
-endif
+
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_X86_32BIT_INIT) += string.o
 endif
+
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
 endif