drm/amd/display: Fixed panic during seamless boot.

[why]
get_pixel_clk_frequency_100hz is undefined in clock_source_funcs.

[how]
set function pointer: ".get_pixel_clk_frequency_100hz = get_pixel_clk_frequency_100hz"
Signed-off-by: David Galiffi <David.Galiffi@amd.com>
Reviewed-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_clock_source.c

@@ -1149,7 +1149,8 @@ static uint32_t dcn3_get_pix_clk_dividers(
 static const struct clock_source_funcs dcn3_clk_src_funcs = {
 	.cs_power_down = dce110_clock_source_power_down,
 	.program_pix_clk = dcn3_program_pix_clk,
-	.get_pix_clk_dividers = dcn3_get_pix_clk_dividers
+	.get_pix_clk_dividers = dcn3_get_pix_clk_dividers,
+	.get_pixel_clk_frequency_100hz = get_pixel_clk_frequency_100hz
 };
 #endif
 /*****************************************/