device/device-<msm8916-mainline>: minor cleanup and fixes (MR 1125)

- Cleanup kernel cmdline:
  - earlycon can automatically detect the memory address of
    the UART controller based on the device tree
  - the comma before n8 in console=ttyMSM0,115200,n8 is actually
    invalid so this was not parsed correctly. However, it is the
    default anyway so we might as well remove it completely

- Configure deviceinfo_getty for all devices

- Workaround probe issue of display by adding a softdep on the panel
  module. This allows the display to work when excluding proprietary
  firmware (just a weird side effect, see comment in modprobe.conf...)