efi: Add support for a hello world test program

It is useful to have a basic sanity check for EFI loader support. Add a
'bootefi hello' command which loads HelloWord.efi and runs it under U-Boot.

Signed-off-by: Simon Glass <sjg@chromium.org>
[agraf: Fix documentation, add unfulfilled kconfig dep]
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index 12159dd..f466408 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -7,6 +7,10 @@
 # This file only gets included with CONFIG_EFI_LOADER set, so all
 # object inclusion implicitly depends on it
 
+CFLAGS_helloworld.o := $(CFLAGS_EFI)
+CFLAGS_REMOVE_helloworld.o := $(CFLAGS_NON_EFI)
+
+obj-$(CONFIG_CMD_BOOTEFI_HELLO) += helloworld_efi.o
 obj-y += efi_image_loader.o efi_boottime.o efi_runtime.o efi_console.o
 obj-y += efi_memory.o
 obj-$(CONFIG_LCD) += efi_gop.o