efi_loader: Add efi-next git tree to MAINTAINERS file

The efi-next tree lives on github, not the usual denx git.
Reflect this in the MAINTAINERS file so that people can
find it.

Signed-off-by: Alexander Graf <agraf@suse.de>

MAINTAINERS

@@ -264,6 +264,7 @@ F:	test/dm/
 EFI PAYLOAD
 M:	Alexander Graf <agraf@suse.de>
 S:	Maintained
+T:	git git://github.com/agraf/u-boot.git
 F:	include/efi_loader.h
 F:	lib/efi_loader/
 F:	cmd/bootefi.c