Fix underlying problem with xscale icache and dcache commands

Fix underlying problem with xscale icache and dcache commands

Fix problem with the xscale icache and dcache commands.  Both commands were
enabling or disabling the mmu, not the caches

I didn't look any further after my earlier patch fixed the trivial problem
with command argument parsing.  Turns out the underlying code was broken.

The resolution is straightforward when you look at the arguments to
xscale_enable_mmu_caches() and xscale_disable_mmu_caches().  I finally
took a deeper look after dumping the cp15 control register (XSCALE_CTRL)
and seeing that the cache bits weren't changing, but the mmu bit was
(which caused all manner of grief, as you can imagine).  This has been
tested and works OK now.

 src/target/xscale.c |   17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>