msm: mdss: primary panel config from boot param

Add ability to read kernel's boot parameters to
check for primary panel interface and panel
configuration. The parameter passes three
fields of information which are parsed by the MDP
driver as a part of the device probe.

Format for cmdline param expected is:
"mdss_mdp.panel=<lk_cfg>:<pan_intf>:<dt_node_name_panel>"
where <lk_cfg> is "1" - lk/gcdb config or "0" non-lk/non-gcdb
config;
<pan_intf> is one of "dsi:<ctrl_id>", "hdmi", "edp";
and <dt_node_name_panel> is the string identical to panel's
device node name from the DT.

Change-Id: Ib9e7e4b69c62537f551aaf9ccaf0dd69eddd6889
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>