drm/amd/display: guard DPPHY_Internal_ctrl

[why]
this register not exist in some asic, based on request remove this from
dc.

[how]
add guard for sanization.
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_link_encoder.h

@@ -62,11 +62,11 @@
 	SRI(DP_DPHY_FAST_TRAINING, DP, id), \
 	SRI(DP_SEC_CNTL1, DP, id), \
 	SRI(DP_DPHY_BS_SR_SWAP_CNTL, DP, id), \
-	SRI(DP_DPHY_INTERNAL_CTRL, DP, id), \
 	SRI(DP_DPHY_HBR2_PATTERN_CONTROL, DP, id)
 
 
 #define LE_DCN10_REG_LIST(id)\
+	SRI(DP_DPHY_INTERNAL_CTRL, DP, id), \
 	LE_DCN_COMMON_REG_LIST(id)
 
 struct dcn10_link_enc_aux_registers {