net/smc: Print function name in smcr_link_down tracepoint

net/smc: Print function name in smcr_link_down tracepoint

This makes the output of smcr_link_down tracepoint easier to use and
understand without additional translating function's pointer address.

It prints the function name with offset:

  <idle>-0       [000] ..s.    69.087164: smcr_link_down: lnk=00000000dab41cdc lgr=000000007d5d8e24 state=0 rc=1 dev=mlx5_0 location=smc_wr_tx_tasklet_fn+0x5ef/0x6f0 [smc]

Link: https://lore.kernel.org/netdev/11f17a34-fd35-f2ec-3f20-dd0c34e55fde@linux.ibm.com/
Signed-off-by: Tony Lu <tonylu@linux.alibaba.com>
Reviewed-by: Wen Gu <guwen@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>