MAINTAINERS: remove myself as maintainer of SMC

I changed responsibilities some time ago, its time
to remove myself as maintainer of the SMC component.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Wenjia Zhang <wenjia@linux.ibm.com>
Link: https://lore.kernel.org/r/20231207202358.53502-1-wenjia@linux.ibm.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>