drm/msm/dsi-staging: reduce log level for phy error while ULPS exit

In certain instances DSI PHY might not be able to cleanly exit
ULPS. This is unavoidable and non fatal. During such cases, clear
phy error status register and avoid logging this error.

Change-Id: I4700adc411bc6b79d1df4d99df8bfdecf82c734d
Signed-off-by: Abhijith Desai <desaia@codeaurora.org>
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>