dtc: ensure #line directives don't consume data from the next line

Previously, the #line parsing regex ended with ({WS}+[0-9]+)?. The {WS}
could match line-break characters. If the #line directive did not contain
the optional flags field at the end, this could cause any integer data on
the next line to be consumed as part of the #line directive parsing. This
could cause syntax errors (i.e. #line parsing consuming the leading 0
from a hex literal 0x1234, leaving x1234 to be parsed as cell data,
which is a syntax error), or invalid compilation results (i.e. simply
consuming literal 1234 as part of the #line processing, thus removing it
from the cell data).

Fix this by replacing {WS} with [ \t] so that it can't match line-breaks.

Convert all instances of {WS}, even though the other instances should be
irrelevant for any well-formed #line directive. This is done for
consistency and ultimate safety.

[Cherry picked from DTC commit a1ee6f068e1c8dbc62873645037a353d7852d5cc]
Reported-by: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

scripts/dtc/dtc-lexer.l

@@ -71,7 +71,7 @@ static int pop_input_file(void);
 			push_input_file(name);
 		}
 
-<*>^"#"(line)?{WS}+[0-9]+{WS}+{STRING}({WS}+[0-9]+)? {
+<*>^"#"(line)?[ \t]+[0-9]+[ \t]+{STRING}([ \t]+[0-9]+)? {
 			char *line, *tmp, *fn;
 			/* skip text before line # */
 			line = yytext;