phy: rockchip: emmc, add vendor prefix to dts properties

phy: rockchip: emmc, add vendor prefix to dts properties

Update the implementation add "rockchip," vendor prefix for the
optional dts properties. Prefix referred from vendor-prefixes.yaml.
Follow up with
commit 8b5c2b45b8f0a ("phy: rockchip: set pulldown for strobe line in dts")
commit a8cef928276bb ("phy: rockchip-emmc: output tap delay dt property")

Signed-off-by: Chris Ruehl <chris.ruehl@gtsys.com.hk>
Link: https://lore.kernel.org/r/20201215014409.905-3-chris.ruehl@gtsys.com.hk
Signed-off-by: Vinod Koul <vkoul@kernel.org>