doc: man-page for bootefi command

Provide a description of the bootefi command.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 127e30c..8675965 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -679,6 +679,7 @@
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-efi.git
 F:	doc/api/efi.rst
 F:	doc/uefi/*
+F:	doc/usage/bootefi.rst
 F:	drivers/rtc/emul_rtc.c
 F:	include/capitalization.h
 F:	include/charset.h