MAINTAINERS: assign include/charset.h

Assign include/charset.h to EFI PAYLOAD.

The functions defined in this include are used by the UEFI sub-system.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 33fd465..c41bc89 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -476,6 +476,7 @@
 F:	doc/README.iscsi
 F:	Documentation/efi.rst
 F:	include/capitalization.h
+F:	include/charset.h
 F:	include/cp1250.h
 F:	include/cp437.h
 F:	include/efi*