target: msm8996: skip splash when panel name is one empty string

Panel name in bootloader can be one empty string after flashing
new image. This empty string will enable static splash in one
uncertain status. So such case should be blocked.

Change-Id: I5a72c3cdf5e22e3f2e2b421a72d948933a527419
Signed-off-by: Guchun Chen <guchunc@codeaurora.org>