msm: mdss: change default value of minimum refresh rate to 48

Most of the DSI panels do not support refresh rate lesser than 48.
So change the default value to 48.

Change-Id: Id47fe3488d7cd85b1eefaea18f3a7b9e6e8b3e31
Signed-off-by: Prashant Nukala <pnukala@codeaurora.org>
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>
Signed-off-by: Bharat Pawar <bpawar@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>