drm/xe: Convert gt suspend/resume messages to debug

Let's be quieter on production configuration and let's also
print the entry point of the gt suspend when debug messages
are enabled.

Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240318180141.267458-1-rodrigo.vivi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>