fault-inject: export setup_fault_attr()

mmc_core module needs to use setup_fault_attr() in order
to set fault injection attributes during module load time.

Signed-off-by: Per Forlin <per.forlin@linaro.org>
Reviewed-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Chris Ball <cjb@laptop.org>