efi_loader: make the UEFI boot manager configurable

Some boards are very tight on the binary size. Booting via UEFI is possible
without using the boot manager.

Provide a configuration option to make the boot manager available.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index 0216eb8..a6355d2 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -21,7 +21,7 @@
 endif
 
 obj-$(CONFIG_CMD_BOOTEFI_HELLO) += helloworld_efi.o
-obj-y += efi_bootmgr.o
+obj-$(CONFIG_CMD_BOOTEFI_BOOTMGR) += efi_bootmgr.o
 obj-y += efi_boottime.o
 obj-$(CONFIG_EFI_HAVE_CAPSULE_SUPPORT) += efi_capsule.o
 obj-$(CONFIG_EFI_CAPSULE_FIRMWARE) += efi_firmware.o