RDMA/hns: Remove return value checks of debugfs functions

driver inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8DJVZ



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It's suggested that the errors returned by debugfs functions should
be ignored, as these functions can handle an error dentry. So remove
all the return value checks.

Fixes: 9bde3d2b912f ("RDMA/hns: Support SW stats with debugfs")
Fixes: a2178118 ("RDMA/hns: Add debugfs support for DCA")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>