net: napi: remove useless stack trace

Whenever a buggy NAPI driver returns more than its budget,
we emit a stack trace that is of no use, since it does not
tell which driver is buggy.

Instead, emit a message giving the function name, and a
descriptive message.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>