checkpatch: Remove checks relating to [smp_]read_barrier_depends()

The [smp_]read_barrier_depends() macros no longer exist, so we don't
need to deal with them in the checkpatch script.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

scripts/checkpatch.pl

@@ -5903,8 +5903,7 @@ sub process {
 		my $barriers = qr{
 			mb|
 			rmb|
-			wmb|
-			read_barrier_depends
+			wmb
 		}x;
 		my $barrier_stems = qr{
 			mb__before_atomic|
@@ -5953,12 +5952,6 @@ sub process {
 			}
 		}
 
-# check for smp_read_barrier_depends and read_barrier_depends
-		if (!$file && $line =~ /\b(smp_|)read_barrier_depends\s*\(/) {
-			WARN("READ_BARRIER_DEPENDS",
-			     "$1read_barrier_depends should only be used in READ_ONCE or DEC Alpha code\n" . $herecurr);
-		}
-
 # check of hardware specific defines
 		if ($line =~ m@^.\s*\#\s*if.*\b(__i386__|__powerpc64__|__sun__|__s390x__)\b@ && $realfile !~ m@include/asm-@) {
 			CHK("ARCH_DEFINES",