libhugetlbfs: Make cross-devel recognize all ix86 arches

In a non-native cross-development scenario, the Makefile
only recognized i386 or x86_64 PC architectures.
Extended this to also recognize i486, i586, and i686

Upstream Status: Accepted but not yet applied by libhugetlbfs project

Signed-off-by: Gary S. Robertson <gary.robertson@linaro.org>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>