MAINTAINERS: Add EFI git repository location

People keep asking for the whereabouts of this git tree, so add it to
MAINTAINERS.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>

MAINTAINERS

@@ -2801,6 +2801,7 @@ F:	sound/usb/misc/ua101.c
 EXTENSIBLE FIRMWARE INTERFACE (EFI)
 M:	Matt Fleming <matt.fleming@intel.com>
 L:	linux-efi@vger.kernel.org
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git
 S:	Maintained
 F:	Documentation/x86/efi-stub.txt
 F:	arch/ia64/kernel/efi.c