Bluetooth: Fix Kconfig for Marvell Bluetooth driver

The Marvell driver selects DEBUG_FS and FW_LOADER for its core driver
and that is pointless. Don't select DEBUG_FS since it is either enabled
or not and it is not for the driver to enable it. Also FW_LOADER is
only used within the SDIO driver and so just have that one select the
FW_LOADER option.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>