ext: hal: ti: Add MSP432P4XX SDK

MSP432P4XX SDK is a CMSIS based SDK offered by Texas Instruments
for supporting their Simplelink MSP432P4XX microcontrollers. The
version included in Zephyr is V1.50.00.12 which is a stripped
down version containing only HAL and SoC header support.

Origin: SIMPLELINK-MSP432-SDK
License: BSD 3-Clause
URL: http://www.ti.com/tool/simplelink-msp432-sdk


Version: V1.50.00.12
Purpose: Provides HAL support to MSP432P4XX SoC
Maintained-by: External

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>