As x86_64 has been "demoted" to an ABI definition rather than a concrete
tune file, replace it with core2-64 for the qemux86-64 machine.
Signed-off-by: Darren Hart <dvhart@linux.intel.com> Cc: Richard Purdie <richard.purdie@linuxfoundation.org> Cc: Paul Eggleton <paul.eggleton@intel.com> Cc: Tom Zanussi <tom.zanussi@intel.com> Cc: Nitin Kamble <nitin.a.kamble@intel.com> Cc: Mark Hatle <mark.hatle@windriver.com> Cc: Bruce Ashfield <bruce.ashfield@windriver.com> Cc: Martin Jansa <martin.jansa@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>