Driver: hci_nxp_setup: Support HCI baudrate update

Change running baudrate from `115200` from `3000000`.

Implement the function `bt_h4_vnd_setup` to update the HCI bandrate.

Add Kconfig `BT_H4_NXP_CTLR_WAIT_TIME_AFTER_BAUDRATE_UPDATE` to set
the waiting time after the controller bandrate HCI vendor specific
command sent. It is used to ensure the controller is ready to update
HCI bandrate.

Select `BT_HCI_SETUP` if `BT_H4_NXP_CTLR` is enabled.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>