carl9170: reinit phy after HT settings have changed

The driver has a set of different initvals for 20 MHz
vs dynamic HT2040 operation. Because we can't change
some of the registers "in-flight", the driver needs to
perform a warm reset.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>