drm/xe: Fix xe_device.h

Some explicit includes are needed only from the xe_device.c.
And there is no need for redundant forward declarations.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240507110959.2747-4-michal.wajdeczko@intel.com