OMAPFB: fix framebuffer console colors

omapfb does not currently set pseudo palette correctly for color depths
above 16bpp, making red text invisible, command like
  echo -e '\e[0;31mRED' > /dev/tty1
will display nothing on framebuffer console in 24bpp mode.
This is because temporary variable is declared incorrectly, fix it.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Cc: stable@vger.kernel.org # v3.x
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>