msm: mdss: Do not release all fences when going to doze mode

UI may update in doze mode and there may be tearing when going
from doze to unblank - with respect to synchronization, doze mode
must be treated as on.

Change-Id: I8635b0722bc6294f6850ab28ce43046f81ed49a5
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>