arch: arm: cortex_m: cleanup SW_VECTOR_RELAY_CLIENT dependencies

CPU Cortex-M implies Mainline Cortex-M, therfore, the dependency
on ARMV6_M_ARMV8_M_BASELINE is redundant and can be removed. The
change in this commit is a no-op.

We also add the ARMV6_M_ARMV8_M_BASELINE dependency on option
CPU_CORTEX_M0_HAS_VECTOR_TABLE_REMAP to make sure it cannot be
selected for non Cortex-M Baseline SoCs (at least, not without
a warning).

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>