mmc: dw_mmc-rockchip: correct property names in debug

Following up the device tree fixed in commits e78c6371 ("ARM: dts:
rockchip: Fix DWMMC clocks") and ca9eee95 ("arm64: dts: rockchip:
Fix DWMMC clocks", 2018-02-15), avoid confusion by using the correct
property name in the debug output if clocks are not found.

Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>