Bluetooth: hci_bcm: Fix empty regulator supplies for Intel Macs

The code path for Macs goes through bcm_apple_get_resources(), which
skips over the code that sets up the regulator supplies. As a result,
the call to regulator_bulk_enable() / regulator_bulk_disable() results
in a NULL pointer dereference.

This was reported on the kernel.org Bugzilla, bug 202963.

Unbreak Broadcom Bluetooth support on Intel Macs by checking if the
supplies were set up before enabling or disabling them.

The same does not need to be done for the clocks, as the common clock
framework API checks for NULL pointers.

Fixes: 75d11676 ("Bluetooth: hci_bcm: Add support for regulator supplies")
Cc: <stable@vger.kernel.org> # 5.0.x
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Tested-by: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>