cc3220sf: soc: Update PRCM call to allow use of ROM API

The API in the current SDK version is rom-patched, and uses
prcm.c code in the driverlib directory.

But, the PRCMMCU3200Init() API call should be prefixed by MAP_
to allow the option to use the ROM API in a future TI SDK version.

Signed-off-by: Gil Pitney <gil.pitney@linaro.org>