Bluetooth: bluecard: blink LED during continuous activity

Currently the activity LED is solid on during continuous activity.
Blink the LED during continuous activity to match Windows driver
behavior.

Cards with activity LED:
power LED = solid on when up, off when down
activity LED = blinking during activity, off when idle

Cards without activity LED:
power LED = solid on when up, off when down, blinking during activity
(don't have such a card so I don't know if Windows driver does the same
thing)

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>