Add rather than override PSOC 6 macros
Add rather than override PSOC 6 macros

Use "macros_add" rather than "marcos" so any macros defined by
MCU_PSOC6 are not overwritten.

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