mac80211: (really) fix rates setup on IBSS merge

when an IBSS merge happened, the supported rates for the newly added station
were left empty, causing the rate control module to be initialized with only
the basic rates.

the section of the ibss code which deals with updating supported rates for
an already existing station failed to inform the rate control module about the
new rates. as both minstrel and pid don't have an update function i just use
the init function.

also remove unnecessary (unsigned long long) casts and edit debug message.

Signed-off-by: Bruno Randolf <br1@einfach.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>