soc: intel_adsp: tools: cavstool.py: Make map_regs() shareable

map_reg() depends on args global variable for knowing it should
load a new firmware or just stand by for logging or Zephyr
shell. The map_regs() code is the very first step to access the
DSP memory, it nees to be shareable if the code is to be accessed
from another python module.

Signed-off-by: Jyri Sarha <jyri.sarha@linux.intel.com>