MAINTAINERS: Add include/hw/input/pl050.h to the PrimeCell/CMSDK section

The corresponding pl050.c file is already listed here, so we should
mention the header here, too.

Message-ID: <20231020060936.524988-2-thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

MAINTAINERS

@@ -657,6 +657,7 @@ F: include/hw/dma/pl080.h
 F: hw/dma/pl330.c
 F: hw/gpio/pl061.c
 F: hw/input/pl050.c
+F: include/hw/input/pl050.h
 F: hw/intc/pl190.c
 F: hw/sd/pl181.c
 F: hw/ssi/pl022.c