msm: mdss: support frame buffer allocation on 8x10

The pan display api is using the frame buffer allocated
from the display driver.  This change is to use the
splash screen memory as frame buffer.

Change-Id: I2560aa644c92145658ac4e873ba6d2e58c5f502a
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>