msm_fb: display: Copy splash image to kernel memory

The bootloader memory from which the splashscreen is shown
gets reclaimed before frame update happens from framework.
Hence, copy the splash image to a local buffer as soon as
display is initialized. This will ensure proper continuous
splashscreen functionality.

CRs-Fixed: 378721
Change-Id: I55a7b97eeced56d2f108d34998d58966610c4305
Signed-off-by: Pradeep Jilagam <pjilagam@codeaurora.org>