target: add support for disabling continuous-splash

This support would be helpful in enabling/disabling continuous
splash screen through fastboot oem command. It can be used
in the following way.
    * fastboot oem select-display-panel <panel_name>:<0/1>
      0 - disable continuous splash, 1 - enable continuous splash
    * fastboot oem select-display-panel <panel_name>
      This will continue to select the panel with default continuous
      splash settings.

Change-Id: Ic1a1a41b7f675b6d1acf2f088e85cb9aad332c0d
7 files changed