arm: v2m musca: Add support for v2m musca SoC and board

Support musca board as a variant, it is a Cortex-M33 based SoC.

Signed-off-by: Karl Zhang <karl.zhang@linaro.org>
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>