soc: mimxrt1064: Add HAL clock header include

The low power mode logic for i.MX RT1064 indirectly includes the HAL
definitions, but this is fragile and depends on specific Kconfig options.

This fixes build issues if for example CONFIG_ARM_MPU is not set.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>