Bluetooth: hciuart: add nvmem dependency

When the hci support is built-in, but mvmem is a loadable module, we
get a link failure:

drivers/bluetooth/hci_ll.o: In function `hci_ti_probe':
hci_ll.c:(.text+0x226): undefined reference to `nvmem_cell_get'
hci_ll.c:(.text+0x238): undefined reference to `nvmem_cell_read'
hci_ll.c:(.text+0x244): undefined reference to `nvmem_cell_put'

This adds another Kconfig dependency to enforce valid configurations.

Fixes: 0e58d0cd ("Bluetooth: hci_ll: Add optional nvmem BD address source")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>