msm: mdss: remove panel type check for split display case.

Split display flag is derived from dsi controller configuration
specified at dtsi. Therefore no need to add checking panel
type at FB registration.

Change-Id: I5b60656c1f5724bdc358d743b8d7600d5beba0b3
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>