linux-imx

selftests: check hot-pluggagble memory for memory-hotplug test

Check for hot-pluggable memory availability in prerequisite() of the
memory-hotplug test.

Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>