iwl3945: reduce debug noise when default debug flags used

iwl3945: reduce debug noise when default debug flags used

Significant literature suggests users use debug flags 0x43fff - this causes
the debug flags to be set that causes information to be printed for every
received frame - including beacons. In the best case it fills up the logs,
at worst it slows driver down and causes failures due to timeouts.

In the RX handler, print debugging only if user requested RX debugging.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>