rockchip: mmc: update MAINTAINERS

The Rockchip-specific wrappers to the DW-MMC and the SDHCI driver
were not covered as part of what's maintained by the architecture
maintainers.  Add them here.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

MAINTAINERS

@@ -159,6 +159,8 @@ F:	board/rockchip/
 F:	drivers/clk/rockchip/
 F:	drivers/gpio/rk_gpio.c
 F:	drivers/misc/rockchip-efuse.c
+F:	drivers/mmc/rockchip_sdhci.c
+F:	drivers/mmc/rockchip_dw_mmc.c
 F:	drivers/pinctrl/rockchip/
 F:	drivers/ram/rockchip/
 F:	drivers/sysreset/sysreset_rockchip.c