Added GPIO is "Thermal and External Power Detect". It's uncertain if this
GPIO is set on GPU initialization or only if a change is detected by the
GPU at runtime.

This GPIO can be found in Rankine and Curie and rarely on Tesla GPUs
VBIOS.

Untested, wrote according to documentation.
Signed-off-by: Mark Menzynski <mmenzyns@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>