fbdev: omapfb: cleanup inconsistent indentation

This cleans up the indentation according to the Linux kernel coding
style, and should fix the warning created by the kernel test robot.

Fixes: 8b08cf2b ("OMAP: add TI OMAP framebuffer driver")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Lucy Mielke <mielkesteven@icloud.com>
Signed-off-by: Helge Deller <deller@gmx.de>