mwl8k: Traffic to clients gets affected when one client leaves a cyrpto bss

When a client disassociates from a crypto enabled bss, data traffic to
other clients connected to the bss is stalled. This was due to a boolean
variable used to keep track if HW crypto is enabled i.e. if set key has
been called to add a key.  This flag was being reset every time delete
key was called e.g when a station leaves the bss. Once the flag is
reset, rx status flags were not being set for connected clients which
disrupts traffic to these clients. Fix this issue by not resetting the
flag since we do not need to reset this flag during the life time of the
bss.

Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>