msm: mdss: dsi: increase dsi error count only for valid errors

Currently, dsi isr error handling routine has a logic to keep
track of the last 5 errors and if the time delta between the first
and the last error is less than 100ms, it invokes an explicit
panic to capture the system state for continuous errors in a short
span of time. However there are few exception error cases which
are expected. Avoid adding the dsi error count on such cases.

Change-Id: Ic2b0e05de15c74bc491109b2b462332c3f48fd87
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>