tools lib api: Renaming pr_warning to pr_warn

tools lib api: Renaming pr_warning to pr_warn

For kernel logging macro, pr_warning is completely removed and
replaced by pr_warn, using pr_warn in tools lib api for symmetry
to kernel logging macro, then we could drop pr_warning in the
whole linux code.

Changing __pr_warning to __pr_warn to be consistent.

Link: http://lkml.kernel.org/r/20191018031850.48498-30-wangkefeng.wang@huawei.com
To: linux-kernel@vger.kernel.org
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>