ibft: convert iscsi_ibft module to iscsi boot lib

This patch just converts the iscsi_ibft module to the
iscsi boot sysfs lib module.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Signed-off-by: Peter Jones <pjones@redhat.com>