Bluetooth: hci_bcm: Fix unbalanced pm_runtime_disable()

On ->setup, pm_runtime_enable() is only called if a valid IRQ was found,
but on ->close(), pm_runtime_disable() is called unconditionally.
Disablement of runtime PM is recorded in a counter, so every
pm_runtime_disable() needs to be balanced.  Fix it.

Cc: Frédéric Danis <frederic.danis.oss@gmail.com>
Reported-and-reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>