msm: mdss: update min prefill lines for msm8937

Update the minimum prefill lines and pixel ram size
for msm8937 as per System Team's recommendations.

Change-Id: Ia0f280fc602ead9eb526ef116f0208f6996375f8
Signed-off-by: Krishna Chaitanya Devarakonda <kdevarak@codeaurora.org>