dtc: Fix recognition of whitespace characters

At present, the lexer in dtc recognizes only space, tab and newline as
whitespace characters.  This is broken; in particular this means that
dtc will get syntax errors on files with DOS-style (CR-LF) newlines.

This patch fixes the problem, using flex's built-int [:space:]
character class.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

dtc-lexer.l

@@ -27,7 +27,7 @@
 
 PROPCHAR	[a-zA-Z0-9,._+*#?-]
 UNITCHAR	[0-9a-f,]
-WS		[ \t\n]
+WS		[[:space:]]
 
 REFCHAR		({PROPCHAR}|{UNITCHAR}|[/@])