msm: mdss: fix smem_len value in quick boot mode

Quick boot mode uses smem_len to allocate buffers
for pan display. And will not display any charging
animation in case of zero smem_len value. Hence avoid
to set smem_len to zero.

Change-Id: I3ffb1373b488e1a5560efe2de33c009f64a1fb4d
Signed-off-by: Ramakant Singh <ramaka@codeaurora.org>