msm: mdss: Handling possible integer overflow

fudge_factor calculation can suffer from integer overflow as numer and
denom are user controlled. Hence this change will first check for the
overflow and return immediately.

CRs-Fixed: 1110860
Change-Id: I3fab3edd4515d7a4c67f29d68b2039f234b03612
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>