tests/amdgpu/amd_hotplug: Check the suspend state after resume

[Why & How]
Check the last hardware sleep state after resume to make sure
last suspend really reached hardware sleep state.

Make sure to enable the suspend related settings in kernel config

Linux Kernel Configuration
└─>Power management and ACPI options
Suspend to RAM and standby
ACPI (Advanced Configuration and Power Interface) Support

Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>