M2351: Change base target name 'NU_PFM_M2351_CM' to 'NU_PFM_M2351'
M2351: Change base target name 'NU_PFM_M2351_CM' to 'NU_PFM_M2351'

This is to meet platform name 'NU_PFM_M2351' registered in mbed-os-tools. This tool
uses the platform name as a key to search platform related properties in targets.json.
For example, the property 'forced_reset_timeout' is critical for Greentea test.

kjbracey-arm/mbed,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed