checkpatch: add --strict test for concatenated string elements

Using a space between concatenated string elements is easier for a human
to read.

ie:
	"String"FOO"bar"

is easier to read as:

	"String" FOO "bar"

So suggest this style with a --strict command line option.
Signed-off-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

@@ -4344,6 +4344,12 @@ sub process {
 			     "Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt\n" . $herecurr);
 		}
 
+# concatenated string without spaces between elements
+		if ($line =~ /"X+"[A-Z_]+/ || $line =~ /[A-Z_]+"X+"/) {
+			CHK("CONCATENATED_STRING",
+			    "Concatenated strings should use spaces between elements\n" . $herecurr);
+		}
+
 # warn about #if 0
 		if ($line =~ /^.\s*\#\s*if\s+0\b/) {
 			CHK("REDUNDANT_CODE",