ANDROID: GKI: export thermal_cdev_update

This export was removed by the upstream commit 6390383b
("thermal/core: Remove unneeded EXPORT_SYMBOLS") since it's only used by
the thermal frameworks. Pixel 6 is using this symbol for it's external
thermal driver module and is needed for GKI testing.

Bug: 242078480
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I5f704055f53816c1e3fdfd776c2d253dffbdab72
Signed-off-by: Lee Jones <joneslee@google.com>