Revert "checkpatch: Error out if deprecated RCU API used"

The definition for single-argument kfree_rcu() has been removed,
so that any further attempt to use it will result in a build error.
Because of this build error, there is no longer any need for a special
check in checkpatch.pl.

Therefore, revert commit 1eacac3.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: joelagnel

scripts/checkpatch.pl

@@ -6427,15 +6427,6 @@ sub process {
 			}
 		}
 
-# check for soon-to-be-deprecated single-argument k[v]free_rcu() API
-		if ($line =~ /\bk[v]?free_rcu\s*\([^(]+\)/) {
-			if ($line =~ /\bk[v]?free_rcu\s*\([^,]+\)/) {
-				ERROR("DEPRECATED_API",
-				      "Single-argument k[v]free_rcu() API is deprecated, please pass rcu_head object or call k[v]free_rcu_mightsleep()." . $herecurr);
-			}
-		}
-
-
 # check for unnecessary "Out of Memory" messages
 		if ($line =~ /^\+.*\b$logFunctions\s*\(/ &&
 		    $prevline =~ /^[ \+]\s*if\s*\(\s*(\!\s*|NULL\s*==\s*)?($Lval)(\s*==\s*NULL\s*)?\s*\)/ &&