boards: mimxrt595_evk_cm33: Default REGULATOR to n

Do not CONFIG_REGULATOR to y unless CONFIG_PM is enabled.
I.e., remove CONFIG_REGULATOR=y from board defconfig because
it is not needed for the board to function, the default
configuration is fine and the regulator is only needed
for additional functionality.

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