freedreno: Add missing va_end.
Fix warning reported by Coverity Scan. Missing varargs init or cleanup (VARARGS) missing_va_end: va_end was not called for ap. Fixes: a0ca1462 ("freedreno: add logging infrastructure") Signed-off-by:Vinson Lee <vlee@freedesktop.org> Part-of: <mesa/mesa!5221> (cherry picked from commit 755c0400)