boot: Add Kconfigs for BOOTMETH_VBE_REQUEST

Allow this to be enabled separately in U-Boot proper and in SPL, since
it is not needed in SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/Makefile b/boot/Makefile
index b9a1223..88193a1 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -52,7 +52,8 @@
 
 obj-$(CONFIG_$(SPL_TPL_)EXPO) += expo.o scene.o scene_menu.o
 
-obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE) += vbe.o vbe_request.o
+obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE) += vbe.o
+obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_REQUEST) += vbe_request.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE) += vbe_simple.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_FW) += vbe_simple_fw.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_OS) += vbe_simple_os.o