mdss: mdp: fix linear format validation during perf check

Fix linear format validation check during perf check
which happens during atomic validation stage. Current
invalid check may lead to perf validation failure and
switch to GPU composition.

Change-Id: Ie1782de2f770de9e10e9b25ad1914405402c2f5d
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>