Fixes

  armsoc_driver.c: In function 'ARMSOCScreenInit':
  armsoc_driver.c:1067:8: error: assignment discards 'const' qualifier from pointer target type [-Werror]

and

  drmmode_display.c: In function 'drmmode_set_mode_major':
  drmmode_display.c:357:4: error: passing argument 1 of 'free' discards 'const' qualifier from pointer target type [-Werror]

Signed-off-by: Rob Clark <robdclark@gmail.com>