tools: moveconfig: fix cleanup of defines across multiple lines

Correct the clean-up of such defines that continue across multiple
lines, like follows:

  #define CONFIG_FOO "this continues to the next line " \
          "this line should be removed too" \
          "this line should be removed as well"

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/moveconfig.py b/tools/moveconfig.py
index 2535079..a083714 100755
--- a/tools/moveconfig.py
+++ b/tools/moveconfig.py
@@ -408,6 +408,9 @@
 
     matched = []
     for i, line in enumerate(lines):
+        if i - 1 in matched and lines[i - 1][-2:] == '\\\n':
+            matched.append(i)
+            continue
         for pattern in patterns:
             if pattern.search(line):
                 matched.append(i)