drm/amd/display/dc/gpio/diagnostics/hw_translate_diag: Include our own header containing prototypes

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

drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/diagnostics/hw_translate_diag.c:37:6: warning: no previous prototype for ‘dal_hw_translate_diag_fpga_init’ [-Wmissing-prototypes]

Cc: Harry Wentland <[e-mail]>
Cc: Leo Li <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Cc: "Christian König" <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/gpio/diagnostics/hw_translate_diag.c

···
  */
 
 #include "dm_services.h"
+#include "hw_translate_diag.h"
 #include "include/gpio_types.h"
 
 #include "../hw_translate.h"