msm: mdss: parse panel node information through module_param

Parse the panel node information from kernel command line
argument through module_param API in both MDP drivers.
This removes the "chosen" node parsing in both MDP driver
to get the kernel command line parameter.

CRs-fixed: 546629
Change-Id: I22fc41c2d493945f2886b478ecb49f599bc87c80
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>