mdss: Work around HX8389C bootloader mdss string change

* Hardcoded mdss string in the bootloader command line passed to the
  kernel causes boot to fail on kernels with screen drivers not
  programmed to accept the old/new string. Fix this by checking for the
  presence of either of both strings at boot and initialising the
  display if at least one of them matches.

* Overwrite the old mdss string with the new one if a display with
  the old naming is found.

* Print the the new panel name for the HX8389C display