Read signature before initialzing panel

This patch reads the panel signature before sending the panel's
init command sequence. If the signature doesn't match LK will
not continue with the initializion of the panel.

While this patch might not work for all panels, it works
for the FP2 and FP2.5 LCD panels.

FPIIM-935

Change-Id: If870d7f3f5785d1616dfe2efb106ab13c6718ab2
1 file changed