trace: Define TEST_FAIL and TEST_FAIL_TAG as inline function

trace: Define TEST_FAIL and TEST_FAIL_TAG as inline function

While these macros are usually used in conditions, they can also simply
be used as a statement in order to check whether a certain code path was
taken. In that case, using a macro that turns into a constant 0 may
cause a compiler warning.

Avoid that issue by using a static inline function that returns 0. This
fixes a build regression introduced by f5790e97cd64 ("nl80211: Delay
event processing during command handling").

Fixes: f5790e97cd64 ("nl80211: Delay event processing during command handling")
Reported-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>