net/smc: shorten lgr_cnt initialization

Save a line of code by making use of ATOMIC_INIT() for lgr_cnt.

Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>