net/smc: Rename 'llc_conf_mutex' variable to 'llc_conf_lock' in struct smc_link_group

sangfor inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7809T



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The 'llc_conf_mutex' variable in struct smc_link_group is not a mutex struct,
so rename it to llc_conf_lock.

Signed-off-by: Litao Jiao <jiaolitao@sangfor.com.cn>