msm: mdss: Clear compat structures before copying to user

In the compat layer, the temporary structures used to convert
data from 32bit to 64bit structures need to be set to 0 before
being assigned values.

CRs-Fixed: 1103689
Change-Id: I405500f427f3f4dc4d38a9fb188fece9a31614ca
Signed-off-by: Sravan Kumar D.V.N <sravank1@codeaurora.org>