checkpatch: complain about the use of dsb().

Now that mb() does what we want, dsb() should be discouraged.

Change-Id: Ib8fe8f44f669753c3d91fac3c6e598e117d6d90e
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
(cherry picked from commit 9c0619be7b93ad114d6f33a749d905ddff93df7d)

scripts/checkpatch.pl

@@ -3284,6 +3284,12 @@ sub process {
 			      $herecurr);
 		}
 
+# dsb is too ARMish, and should usually be mb.
+		if ($line =~ /\bdsb\b/) {
+			WARN("Use of dsb is discouranged: prefer mb.\n" .
+			     $herecurr);
+		}
+
 # unbounded string functions are overflow risks
 		my %str_fns = (
 			"sprintf" => "snprintf",