bitbake-prserv-tool: check file name

Fixed:
$ bitbake-prserv-tool import /tmp/1
  File "/path/to/lib/bb/parse/__init__.py", line 114, in handle(fn='/tmp/1', data=<bb.data_smart.DataSmart object at 0x2369bd0>, include=True):
                     return h['handle'](fn, data, include)
    >    raise ParseError("not a BitBake file", fn)

ParseError: ParseError in /tmp/1: not a BitBake file

But 1.conf or 1.inc works well, check the filename and print proper
error message.

(From OE-Core rev: 273eee7a3614caea17c5bc93b720353641293cf7)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/bitbake-prserv-tool

@@ -86,6 +86,15 @@ do_migrate_localcount ()
 
 [ $# -eq 0 ] && help  && exit 1
 
+case $2 in
+*.conf|*.inc)
+    ;;
+*)
+    echo ERROR: $2 must end with .conf or .inc!
+    exit 1
+    ;;
+esac
+
 case $1 in
 export)
     do_export $2