arch: arm: Enable CMSIS-Core for Cortex-R by default

This commit enables the CMSIS-Core(R) processor interface driver for
the Cortex-R platforms by default.

The CMSIS-Core component provides a set of standard interface functions
to control the Cortex-R series processor cores and will be required by
the arch port as well as other CMSIS library components (e.g. CMSIS-DSP
and CMSIS-NN).

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>