checkpatch: Drop pr_warning check

All pr_warning are removed from kernel, let's cleanup pr_warning
check in checkpatch.

Link: http://lkml.kernel.org/r/20191128004752.35268-5-wangkefeng.wang@huawei.com
To: linux-kernel@vger.kernel.org
Cc: gregkh@linuxfoundation.org
Cc: tj@kernel.org
Cc: arnd@arndb.de
Cc: sergey.senozhatsky@gmail.com
Cc: rostedt@goodmis.org
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

scripts/checkpatch.pl

@@ -4121,15 +4121,6 @@ sub process {
 			     "Prefer [subsystem eg: netdev]_$level2([subsystem]dev, ... then dev_$level2(dev, ... then pr_$level(...  to printk(KERN_$orig ...\n" . $herecurr);
 		}
 
-		if ($line =~ /\bpr_warning\s*\(/) {
-			if (WARN("PREFER_PR_LEVEL",
-				 "Prefer pr_warn(... to pr_warning(...\n" . $herecurr) &&
-			    $fix) {
-				$fixed[$fixlinenr] =~
-				    s/\bpr_warning\b/pr_warn/;
-			}
-		}
-
 		if ($line =~ /\bdev_printk\s*\(\s*KERN_([A-Z]+)/) {
 			my $orig = $1;
 			my $level = lc($orig);