rename swupdate_auto_versions to swupdate_get_pkgvar

It is now possible to get any variable of any package by calling the
function, so give it a more appropriate name.

Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Thomas Haemmerle <thomas.haemmerle@leica-geosystems.com>

classes/swupdate-lib.bbclass

@@ -75,7 +75,7 @@ def swupdate_sign_file(d, s, filename):
 
     return hash
 
-def swupdate_auto_versions(d, s, parms):
+def swupdate_get_pkgvar(d, s, parms):
     import re
     import oe.packagedata