MAINTAINERS: Add Siqueira for AMD DC

He's been helping maintain it for quite a while now. Make
it official.
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

MAINTAINERS

@@ -902,6 +902,7 @@ F:	include/uapi/linux/psp-sev.h
 AMD DISPLAY CORE
 M:	Harry Wentland <harry.wentland@amd.com>
 M:	Leo Li <sunpeng.li@amd.com>
+M:	Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
 L:	amd-gfx@lists.freedesktop.org
 S:	Supported
 T:	git https://gitlab.freedesktop.org/agd5f/linux.git