checkpatch: struct file_operations should normally be const

In the general use case struct file_operations should be a const object.
Check for and warn where it is not.  As suggested by Steven and Ingo.

Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2509,6 +2509,11 @@ sub process {
 		if ($line =~ /^.\s*__initcall\s*\(/) {
 			WARN("please use device_initcall() instead of __initcall()\n" . $herecurr);
 		}
+# check for struct file_operations, ensure they are const.
+		if ($line =~ /\bstruct\s+file_operations\b/ &&
+		    $line !~ /\bconst\b/) {
+			WARN("struct file_operations should normally be const\n" . $herecurr);
+		}
 
 # use of NR_CPUS is usually wrong
 # ignore definitions of NR_CPUS and usage to define arrays as likely right