net: wireless: bcmdhd: Fix driver hang when resetting

net: wireless: bcmdhd: Fix driver hang when resetting

bus->tx_max was not being initialized when we do a reset and
the driver is statically linked.  this led to about a 50%
chance that it would be considered an illegal value when
we send the mac address to the FW.  add code to initialize
it to a safe value until we receive the right value from the fw.

Bug: 5974574

Change-Id: I28ab25d97203ef075e5354c25f85a25daaff5594
Signed-off-by: Mike J. Chen <mjchen@google.com>
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>