drm/amdgpu: Allow to reset to EERPOM table.

The table grows quickly during debug/development effort when
multiple RAS errors are injected. Allow to avoid this by setting
table header back to empty if needed.

v2: Switch to debugfs entry instead of load time parameter.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>