dtc: Reinstate full old-style reference-to-path for v0 dts files

Commit 7c44c2f9cb broke backwards
compatibility more badly than I realised.  Contrary to what I thought
there are in-kernel, in-use dts files which relied on
references-to-path with paths including a comma, which no longer
compile after that commit.

So, this patch reinstates full support for bare references-to-path in
dts-v0 input.  This means there will be some rather surprising lexical
corner cases when using path-expanded references in v0 files.  But,
since path-expanded references are new, v0 files shouldn't typically
be using them anyway.  If the corner cases cause a problem, you can
always convert to dts-v1 which handles the lexical issues here more
nicely.

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

dtc-lexer.l

@@ -27,7 +27,6 @@
 
 PROPNODECHAR	[a-zA-Z0-9,._+*#?@-]
 PATHCHAR	({PROPNODECHAR}|[/])
-LEGACYPATHCHAR	[a-zA-Z0-9_@/]
 LABEL		[a-zA-Z_][a-zA-Z0-9_]*
 
 %{
@@ -158,7 +157,7 @@ static int dts_version; /* = 0 */
 			return DT_REF;
 		}
 
-<INITIAL>"&/"{LEGACYPATHCHAR}+ {	/* old-style path reference */
+<INITIAL>"&/"{PATHCHAR}+ {	/* old-style path reference */
 			yylloc.filenum = srcpos_filenum;
 			yylloc.first_line = yylineno;
 			DPRINT("Ref: %s\n", yytext+1);