drm/amdgpu/dce8: simplify hpd code

Use an address offset like other dce code.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/cikd.h

@@ -43,6 +43,14 @@
 #define CRTC4_REGISTER_OFFSET                 (0x477c - 0x1b7c)
 #define CRTC5_REGISTER_OFFSET                 (0x4a7c - 0x1b7c)
 
+/* hpd instance offsets */
+#define HPD0_REGISTER_OFFSET                 (0x1807 - 0x1807)
+#define HPD1_REGISTER_OFFSET                 (0x180a - 0x1807)
+#define HPD2_REGISTER_OFFSET                 (0x180d - 0x1807)
+#define HPD3_REGISTER_OFFSET                 (0x1810 - 0x1807)
+#define HPD4_REGISTER_OFFSET                 (0x1813 - 0x1807)
+#define HPD5_REGISTER_OFFSET                 (0x1816 - 0x1807)
+
 #define BONAIRE_GB_ADDR_CONFIG_GOLDEN        0x12010001
 #define HAWAII_GB_ADDR_CONFIG_GOLDEN         0x12011003