efivarfs: Move to fs/efivarfs

Now that efivarfs uses the efivar API, move it out of efivars.c and
into fs/efivarfs where it belongs. This move will eventually allow us
to enable the efivarfs code without having to also enable
CONFIG_EFI_VARS built, and vice versa.

Furthermore, things like,

    mount -t efivarfs none /sys/firmware/efi/efivars

will now work if efivarfs is built as a module without requiring the
use of MODULE_ALIAS(), which would have been necessary when the
efivarfs code was part of efivars.c.

Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Jeremy Kerr <jk@ozlabs.org>
Reviewed-by: Tom Gundersen <teg@jklm.no>
Tested-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

MAINTAINERS

@@ -2990,6 +2990,15 @@ F:	arch/x86/platform/efi/*
 F:	drivers/firmware/efivars.c
 F:	include/linux/efi*.h
 
+EFI VARIABLE FILESYSTEM
+M:	Matthew Garrett <matthew.garrett@nebula.com>
+M:	Jeremy Kerr <jk@ozlabs.org>
+M:	Matt Fleming <matt.fleming@intel.com>
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git
+L:	linux-efi@vger.kernel.org
+S:	Maintained
+F:	fs/efivarfs/
+
 EFIFB FRAMEBUFFER DRIVER
 L:	linux-fbdev@vger.kernel.org
 M:	Peter Jones <pjones@redhat.com>