Various siteinfo files: Consolidate va_copy/__va_copy/va_val_copy

Various siteinfo files: Consolidate va_copy/__va_copy/va_val_copy

Providing va_copy / __va_copy come down to the libc.  va_val_copy
comes down to the architecture.  Unfortunately it's assumed true
if not set, so we need to make sure to set this to false for
x86_64 where it is not true.

(From OE-Core rev: a54a803ed89969c2416bfa9d911fe4cf558e2391)

Signed-off-by: Tom Rini <tom_rini@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>