xbmc: append +gitr${SRCPV} to PV not PR

* otherwise AUTOINC in SRCPV isn't expanded and stays in PKGR and
  filename
* I haven't seen it documented anywhere, but oe-core is full of checks
  like this:
  meta/classes/migrate_localcount.bbclass: if not 'AUTOINC' in pv:
  meta/classes/package.bbclass:            if 'AUTOINC' in pkgv:
  meta/classes/prexport.bbclass:           if 'AUTOINC' in ver:
  meta/classes/prserv.bbclass:             if 'AUTOINC' in pv:
  so it looks intentional

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>