west: Add cmsis-dsp fix for shifting by negative amounts

This patch has been accepted upstream https://github.com/ARM-software/CMSIS-DSP/pull/265 and
into the Zephyr module https://github.com/zephyrproject-rtos/cmsis-dsp/pull/7



This PR is ready for review and merging.

Signed-off-by: Keith Packard <keithp@keithp.com>