staging: sm750fb: remove PANEL_DISPLAY_CTRL_TFT_DISP defines

The PANEL_DISPLAY_CTRL_TFT_DISP definitions artificially encode
PANEL_DISPLAY_CTRL_DUAL_DISPLAY and PANEL_DISPLAY_CTRL_DOUBLE_PIXEL bits
combinations. Replace the PANEL_DISPLAY_CTRL_TFT_DISP usage with direct use
of the bits defined in the datasheet.

Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>