drm/msm/mdp5: Update SSPP_MAX value

'SSPP_MAX + 1' is the max number of hwpipes that can be present on a
MDP5 platform. Recently, 2 new cursor hwpipes were added, which
caused overflows in arrays that used SSPP_MAX to represent the number
of elements. Update the SSPP_MAX value to incorporate the extra
hwpipes.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>