drm/amd/display: add sanity check for clk table from smu

[Why]
Handle the case where we don't get a valid table. Also fixes compiler
warning for variable potentially used before assignment.

[How]
If the entire table has no valid fclk, reject the table and use our own
hard code.
Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -546,6 +546,8 @@ void rn_clk_mgr_helper_populate_bw_params(struct clk_bw_params *bw_params, struc
 {
 	int i, j = 0;
 
+	j = -1;
+
 	ASSERT(PP_SMU_NUM_FCLK_DPM_LEVELS <= MAX_NUM_DPM_LVL);
 
 	/* Find lowest DPM, FCLK is filled in reverse order*/
@@ -557,6 +559,12 @@ void rn_clk_mgr_helper_populate_bw_params(struct clk_bw_params *bw_params, struc
 		}
 	}
 
+	if (j == -1) {
+		/* clock table is all 0s, just use our own hardcode */
+		ASSERT(0);
+		return;
+	}
+
 	bw_params->clk_table.num_entries = j + 1;
 
 	for (i = 0; i < bw_params->clk_table.num_entries; i++, j--) {