video: fbdev: atari: Atari 2 bpp (STe) palette bugfix

The code to set the shifter STe palette registers has a long
standing operator precedence bug, manifesting as colors set
on a 2 bits per pixel frame buffer coming up with a distinctive
blue tint.

Add parentheses around the calculation of the per-color palette
data before shifting those into their respective bit field position.

This bug goes back a long way (2.4 days at the very least) so there
won't be a Fixes: tag.

Tested on ARAnyM as well on Falcon030 hardware.

Cc: stable@vger.kernel.org
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/all/CAMuHMdU3ievhXxKR_xi_v3aumnYW7UNUO6qMdhgfyWTyVSsCkQ@mail.gmail.com


Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>