m68k: report correct FPU type on ColdFire MMU platforms

Not all ColdFire SoC parts that have an MMU also have an FPU - so set
an FPU type (via m68k_fputype) appropriate for the configured platform.

With this set correctly /proc/cpuinfo will report FPU "none" on devices
that don't have one. And kernel code paths that initialize FPU hardware
will now only execute if an FPU is actually present.

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