drm/amd/display: Check for null fclk voltage when parsing clock table

[WHY]
In cases where a clock table is malformed such that fclk entries have
frequencies but not voltages listed, we don't catch the error and set
clocks to 0 instead of using hardcoded values as we should.

[HOW]
Add check for clock tables fclk entry's voltage as well

Signed-off-by: Michael Strauss <[e-mail]>
Reviewed-by: Eric Yang <[e-mail]>
Acked-by: Rodrigo Siqueira <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c

···
 	/* Find lowest DPM, FCLK is filled in reverse order*/
 
 	for (i = PP_SMU_NUM_FCLK_DPM_LEVELS - 1; i >= 0; i--) {
-		if (clock_table->FClocks[i].Freq != 0) {
+		if (clock_table->FClocks[i].Freq != 0 && clock_table->FClocks[i].Vol != 0) {
 			j = i;
 			break;
 		}