checkpatch: don't ask for asm/file.h to linux/file.h unconditionally

Currently checkpatch warns when asm/file.h is included and linux/file.h
exists.  That conversion can be made when linux/file.h includes asm/file.h
which is not always the case.(See signal.h)
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Andy Whitcroft <apw@canonical.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -4242,7 +4242,8 @@ sub process {
 			}
 		}
 
-#warn if <asm/foo.h> is #included and <linux/foo.h> is available (uses RAW line)
+# warn if <asm/foo.h> is #included and <linux/foo.h> is available and includes
+# itself <asm/foo.h> (uses RAW line)
 		if ($tree && $rawline =~ m{^.\s*\#\s*include\s*\<asm\/(.*)\.h\>}) {
 			my $file = "$1.h";
 			my $checkfile = "include/linux/$file";
@@ -4250,6 +4251,8 @@ sub process {
 			    $realfile ne $checkfile &&
 			    $1 !~ /$allowed_asm_includes/)
 			{
+				my $asminclude = `grep -Ec "#include\\s+<asm/$file>" $root/$checkfile`;
+				if ($asminclude > 0) {
 					if ($realfile =~ m{^arch/}) {
 						CHK("ARCH_INCLUDE_LINUX",
 						    "Consider using #include <linux/$file> instead of <asm/$file>\n" . $herecurr);
@@ -4259,6 +4262,7 @@ sub process {
 					}
 				}
 			}
+		}
 
 # multi-statement macros should be enclosed in a do while loop, grab the
 # first statement and ensure its the whole macro if its not enclosed