Bluetooth: btbcm: Obtain and handle reset GPIO

Obtain and drive the optional reset GPIO line if this is
not hardwired in the platform. This is needed on the
Samsung GT-I9070 mobile phone.

The invers of power is used, this should be OK to apply
simultaneously as the power signal according to
figures 47-51 on pages 159-161 in the BCM4330 datasheet.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>