mpam/resctrl: Clean up unused function parameter in mkdir path

hulk inclusion
category: cleanup
bugzilla: https://gitee.com/openeuler/kernel/issues/I9PVOZ



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Previous commit ("mpam/resctrl: Fix a deadlock due to inaccurate
reference") changed the argument to resctrl_group_kn_lock_live()/
resctrl_group_kn_unlock() within mkdir_resctrl_prepare(). That change
resulted in an unused function parameter to mkdir_resctrl_prepare().

Clean up the unused function parameter in mkdir_resctrl_prepare() and its
callers resctrl_group_mkdir_mon() and resctrl_group_mkdir_ctrl_mon().

Signed-off-by: Yu Liao <liaoyu15@huawei.com>