drm/amd/display: Fix incorrect size calculation for loop in dcn401

[WHY]
fe_clk_en and be_clk_sel have size of 4 but sizeof(fe_clk_en) has
byte size 16 which is lager than the array size.

[HOW]
Use ARRAY_SIZE for calculating size.

This fixes 2 OVERRUN issues reported by Coverity.

Reviewed-by: Harry Wentland <[e-mail]>
Acked-by: Zaeem Mohamed <[e-mail]>
Signed-off-by: Alex Hung <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dccg/dcn401/dcn401_dccg.c

···
 	/* for DPMST, this backend could be used by multiple front end.
 	only disable the backend if this stream_enc_ins is the last active stream enc connected to this back_end*/
 		uint8_t i;
-		for (i = 0; i != link_enc_inst && i < sizeof(fe_clk_en); i++) {
+		for (i = 0; i != link_enc_inst && i < ARRAY_SIZE(fe_clk_en); i++) {
 			if (fe_clk_en[i] && be_clk_sel[i] == link_enc_inst)
 				num_enabled_symclk_fe++;
 		}