msm: mdss: do not init phy and controller with cont splash enabled

When continuous splash screen feature is enabled, the DSI phy and
controller are configured in the bootloader and left on. In such
cases, we do not need to initialize DSI phy and controller during
probe as it may overwrite the settings and can potentially cause
unexpected behaviors.

Change-Id: Ifdf4579be2a3cd45f71170237e0be193d78dba0f
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>