Bluetooth: Fix endianness of cryptographic toolbox function h8

Convert endianness of supplied parameters before calculating
the AES-CMAC. Bluetooth stores values in little-endian and
crypto traditionally operates on big-endian storage.

Relates to commit e9c542ab ("Bluetooth: Add the
cryptographic toolbox function h8").

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>