boards: mimxrt1040_evk: enable Bluetooth

Add pinmux pinmux_lpuart3_flowcontrol
and pinmux_lpuart3_sleep for HCI-UART.

Add a node m2_hci_uart for HCI_UART.

And add chosen `zephyr,bt-hci =
&bt_hci_uart;`

Update section `Supported Features`,
section `Connections and IOs` and
section `Serial Port` for this feature.

Add section `Fetch Binary Blobs` to
guide how to fetch binary blobs for
BT modules.

add section `Bluetooth Module` for
hardware rework.

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