x86.ini: increase arduino_101 priority

The ordering of the list of platforms is in priority order,
as the sanitycheck --platform-limit option chooses the first
N platforms in this list when doing a run. Move arduino_101 to
second position. qemu_x86_iamcu is still top priority as it
can execute code as part of the tests.

Change-Id: I989d91c66a0a741ce8eebe6279ee4512c33eb5e9
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>