checkpatch: Support wide strings

Allow prefixing typical strings with L for wide strings

Patch originally by Joe Perches
https://lkml.org/lkml/2017/10/17/1117

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

scripts/checkpatch.pl

@@ -392,7 +392,7 @@ our $Binary	= qr{(?i)0b[01]+$Int_type?};
 our $Hex	= qr{(?i)0x[0-9a-f]+$Int_type?};
 our $Int	= qr{[0-9]+$Int_type?};
 our $Octal	= qr{0[0-7]+$Int_type?};
-our $String	= qr{"[X\t]*"};
+our $String	= qr{(?:\bL)?"[X\t]*"};
 our $Float_hex	= qr{(?i)0x[0-9a-f]+p-?[0-9]+[fl]?};
 our $Float_dec	= qr{(?i)(?:[0-9]+\.[0-9]*|[0-9]*\.[0-9]+)(?:e-?[0-9]+)?[fl]?};
 our $Float_int	= qr{(?i)[0-9]+e-?[0-9]+[fl]?};
@@ -5254,13 +5254,14 @@ sub process {
 		}
 
 # concatenated string without spaces between elements
-		if ($line =~ /$String[A-Z_]/ || $line =~ /[A-Za-z0-9_]$String/) {
+		if ($line =~ /$String[A-Z_]/ ||
+		    ($line =~ /([A-Za-z0-9_]+)$String/ && $1 !~ /^L$/)) {
 			CHK("CONCATENATED_STRING",
 			    "Concatenated strings should use spaces between elements\n" . $herecurr);
 		}
 
 # uncoalesced string fragments
-		if ($line =~ /$String\s*"/) {
+		if ($line =~ /$String\s*L?"/) {
 			WARN("STRING_FRAGMENTS",
 			     "Consecutive strings are generally better as a single string\n" . $herecurr);
 		}