msm: mdss: Fix to validate data copied from user space

The overlay zorder values copied from user space are used
as index in left_lm_zo_cnt and right_lm_zo_cnt. This fix
will validate the overlay zorder value copied from user
space to not go beyond MDSS_MDP_MAX_STAGE, thus preventing
any arbitrary increments in kernel memory.

Bug: 30019716
CRs-Fixed: 1049232
Change-Id: Ie8e65ce9f58cb357204bfa4c6a6e0fccec82d5ba
Signed-off-by: Shalini Krishnamoorthi <shakri@codeaurora.org>
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>