[iMX6][LVDS] LVDS resolution configurable via bootargs
Introduced the possibility to configure the LVDS resolution via bootargs (as wa possible into the past). Example of command line:
video=mxcfb0:dev=ldb,LDB-1280P60,datamap=spwg,if=RGB24,bpp=32
Note: this is compatible with seco_config command presents into the our U-Boot version