linux-yocto/3.4: add x32 configuration fragment

linux-yocto/3.4: add x32 configuration fragment

When x32 is the tuning for a x86 MACHINE, the kernel should also have
CONFIG_X86_X32=y. This adds a x32 fragment that can be used to trigger
the right ABI.

The commit also contains a check for mx32 in TUNE_FEATURES, and if
present, the new fragment will be appended to KERNEL_FEATURES and
trigger the support in the kernel.

cc: Saul Wold <sgw@linux.intel.com>
(From OE-Core rev: bf689c60caa905eb8866101b9e99dd4ae246a2ca)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>