mbox: Add NXP MU as a MBOX device

Add a MBOX driver wrapper around the NXP MU, simular to
the existing wrapper around the NXP S32 MRU. This allows Zephyr IPC
to work based on the MU, on a number of NXP boards.

Also update the SHA of NXP HAL to enable the Kconfig for this driver.

Signed-off-by: Yicheng Li <yichengli@google.com>