soc: nxp: mcxw: Switch to soc_reset_hook

Base enablement of MCXW merged while z_arm_platform_init was being
deprecated, resulting situation is now that no platform init is
happening, fix by converting to use soc_reset_hook.

Also fix a comment that said the core was being set to 40 MHz, when it
is actually being set up to 96 MHz.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>