clk: rockchip: Add div50 clock-ids for sdmmc on px30 and nandc

EMMC and SDIO already have these clock-ids (still unused) only sdmmc is
missing them, so fix that.

Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20190917081903.25139-1-heiko@sntech.de