m68k: coldfire: fix breakage of missed IO access update

Fix the last remaining breakage caused by missing a SoC IO access
update. Commit e1f3a00670d1 ("m68k: coldfire: use ColdFire specifc
IO access in SoC code") missed this read16() call which should be
mcf_read16().

Fixes: e1f3a00670d1 ("m68k: coldfire: use ColdFire specifc IO access in SoC code")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202607180731.U4tiwFcQ-lkp@intel.com/
Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>