drm/amd/display: Add missing pflip irq for dcn2.0

If we have more than 4 displays we will run
into dummy irq calls or flip timout issues.
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/irq/dcn20/irq_service_dcn20.c

@@ -299,8 +299,8 @@ irq_source_info_dcn20[DAL_IRQ_SOURCES_NUMBER] = {
 	pflip_int_entry(1),
 	pflip_int_entry(2),
 	pflip_int_entry(3),
-	[DC_IRQ_SOURCE_PFLIP5] = dummy_irq_entry(),
-	[DC_IRQ_SOURCE_PFLIP6] = dummy_irq_entry(),
+	pflip_int_entry(4),
+	pflip_int_entry(5),
 	[DC_IRQ_SOURCE_PFLIP_UNDERLAY0] = dummy_irq_entry(),
 	gpio_pad_int_entry(0),
 	gpio_pad_int_entry(1),