net: smc: fix different types in min()

net: smc: fix different types in min()

Fix build:

 include/linux/minmax.h:45:25: note: in expansion of macro ‘__careful_cmp’
   45 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
 net/smc/smc_tx.c:150:24: note: in expansion of macro ‘min’
  150 |         corking_size = min(sock_net(&smc->sk)->smc.sysctl_autocorking_size,
      |                        ^~~

Fixes: 12bbb0d163a9 ("net/smc: add sysctl for autocorking")
Link: https://lore.kernel.org/r/20220301222446.1271127-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>