msm: mdss: Avoid variable overloading

A particular variable is overloaded and used in 2 different
contexts. This causes overwriting of original value and leads
to incorrect error handling. This code adds a new variable to
avoid such condition.

Change-Id: Ibd040e6b4ce95759cc0011304940365c70e6c12a
Signed-off-by: Shalabh Jain <shalabhj@codeaurora.org>