m68knommu: switch to using IO access methods in WildFire board code

Most ColdFire support code has switched to using IO memory access
methods (readb/writeb/etc) when reading and writing internal peripheral
device registers. The WildFire board specific halt code was missed.

As it is now the WildFire code is broken, since all register definitions
were changed to be register addresses only some time ago.

Fix the WildFire board code to use the appropriate IO access functions.

Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>