target: don't swap MMU/no-MMU work areas

Resolve serious bug inserted by the "target: require working
area for physical/virtual addresses to be specified" patch.
It forced use of (invalid) virtual addresses when the MMU
was disabled, and vice versa.

Observed to break at least Cortex-M3, ARM926, ARM7TDMI whenever
work areas are used, such as during bulk writes to flash, DDR2,
SRAM, and so on.

Also, fix overlong lines and whitespace goofs.

[ Backport from mainline a9abfa7d ]

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