Switch x86/x86-64 -mtune from "atom" to more generic "intel"

-mtune=intel is tradeoff tuning between top IA archs whereas "atom" is
best on atom only.

Change-Id: I27668e4f48f26b00742d117a9a2a38e8903e22d5
Signed-off-by: Pavel Chupin <pavel.v.chupin@intel.com>
Merge remote-tracking branch 'aosp/master'