cmd: add efidebug command

Currently, there is no easy way to add or modify UEFI variables.
In particular, bootmgr supports BootOrder/BootXXXX variables, it is
quite hard to define them as u-boot variables because they are represented
in a complicated and encoded format.

The new command, efidebug, helps address these issues and give us
more friendly interfaces:
 * efidebug boot add: add BootXXXX variable
 * efidebug boot rm: remove BootXXXX variable
 * efidebug boot dump: display all BootXXXX variables
 * efidebug boot next: set BootNext variable
 * efidebug boot order: set/display a boot order (BootOrder)

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 0cce9db..4fabb75 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -471,6 +471,7 @@
 F:	test/py/tests/test_efi*
 F:	test/unicode_ut.c
 F:	cmd/bootefi.c
+F:	cmd/efidebug.c
 F:	cmd/nvedit_efi.c
 F:	tools/file2include.c