efi_loader: rename BOOTEFI_BOOTMGR to EFI_BOOTMGR

At this point, EFI boot manager interfaces is fully independent from
bootefi command. So just rename the configuration parameter.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 64f2f1c..db5571d 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -41,7 +41,7 @@
 	  You may enable CMD_BOOTEFI_BINARY so that you can use bootefi
 	  command to do that.
 
-config BOOTEFI_BOOTMGR
+config EFI_BOOTMGR
 	bool "UEFI Boot Manager"
 	default y
 	select BOOTMETH_GLOBAL if BOOTSTD