iwlwifi: make tracing use device as identifier

Tracing used the priv pointer as an identifier,
which has the problem that we don't have it in
all code, and also some people say no pointers
should be "leaked" to userspace.

Use the device name instead, it is more useful
anyway.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>