m68knommu: fix overwriting of bits in ColdFire V3 cache control

m68knommu: fix overwriting of bits in ColdFire V3 cache control

The Cache Control Register (CACR) of the ColdFire V3 has bits that
control high level caching functions, and also enable/disable the use
of the alternate stack pointer register (the EUSP bit) to provide
separate supervisor and user stack pointer registers. The code as
it is today will blindly clear the EUSP bit on cache actions like
invalidation. So it is broken for this case - and that will result
in failed booting (interrupt entry and exit processing will be
completely hosed).

This only affects ColdFire V3 parts that support the alternate stack
register (like the 5329 for example) - generally speaking new parts do,
older parts don't. It has no impact on ColdFire V3 parts with the single
stack pointer, like the 5307 for example.

Fix the cache bit defines used, so they maintain the EUSP bit when
carrying out cache actions through the CACR register.

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