drm/amd/display/dc/gpio/diagnostics/hw_factory_diag: Fix struct declared...

drm/amd/display/dc/gpio/diagnostics/hw_factory_diag: Fix struct declared inside parameter list error

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:43: warning: ‘struct hw_factory’ declared inside parameter list will not be visible outside of this definition or declaration
 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:6: note: previous declaration of ‘dal_hw_factory_diag_fpga_init’ was here
 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:43: warning: ‘struct hw_factory’ declared inside parameter list will not be visible outside of this definition or declaration
 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:6: note: previous declaration of ‘dal_hw_factory_diag_fpga_init’ was here
 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:43: warning: ‘struct hw_factory’ declared inside parameter list will not be visible outside of this definition or declaration
 drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_factory_diag.h:30:6: note: previous declaration of ‘dal_hw_factory_diag_fpga_init’ was here

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/gpio/diagnostics/hw_factory_diag.h

@@ -26,6 +26,8 @@
 #ifndef __DAL_HW_FACTORY_DIAG_FPGA_H__
 #define __DAL_HW_FACTORY_DIAG_FPGA_H__
 
+struct hw_factory;
+
 /* Initialize HW factory function pointers and pin info */
 void dal_hw_factory_diag_fpga_init(struct hw_factory *factory);