drm/amd/display: Minor refactor of DP PHY test automation

[Why]
Improve readability and maintainability of code.

[How]
Refactor test pattern size calculation out of function
call parameter and store value in variable.
Signed-off-by: George Shen <george.shen@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -2755,9 +2755,10 @@ static void dp_test_send_phy_test_pattern(struct dc_link *link)
 	union phy_test_pattern dpcd_test_pattern;
 	union lane_adjust dpcd_lane_adjustment[2];
 	unsigned char dpcd_post_cursor_2_adjustment = 0;
-	unsigned char test_80_bit_pattern[
+	unsigned char test_pattern_buffer[
 			(DP_TEST_80BIT_CUSTOM_PATTERN_79_72 -
 			DP_TEST_80BIT_CUSTOM_PATTERN_7_0)+1] = {0};
+	unsigned int test_pattern_size = 0;
 	enum dp_test_pattern test_pattern;
 	struct dc_link_training_settings link_settings;
 	union lane_adjust dpcd_lane_adjust;
@@ -2827,12 +2828,15 @@ static void dp_test_send_phy_test_pattern(struct dc_link *link)
 	break;
 	}
 
-	if (test_pattern == DP_TEST_PATTERN_80BIT_CUSTOM)
+	if (test_pattern == DP_TEST_PATTERN_80BIT_CUSTOM) {
+		test_pattern_size = (DP_TEST_80BIT_CUSTOM_PATTERN_79_72 -
+				DP_TEST_80BIT_CUSTOM_PATTERN_7_0) + 1;
 		core_link_read_dpcd(
 				link,
 				DP_TEST_80BIT_CUSTOM_PATTERN_7_0,
-				test_80_bit_pattern,
-				sizeof(test_80_bit_pattern));
+				test_pattern_buffer,
+				test_pattern_size);
+	}
 
 	/* prepare link training settings */
 	link_settings.link = link->cur_link_settings;
@@ -2870,9 +2874,8 @@ static void dp_test_send_phy_test_pattern(struct dc_link *link)
 		test_pattern,
 		DP_TEST_PATTERN_COLOR_SPACE_UNDEFINED,
 		&link_training_settings,
-		test_80_bit_pattern,
-		(DP_TEST_80BIT_CUSTOM_PATTERN_79_72 -
-		DP_TEST_80BIT_CUSTOM_PATTERN_7_0)+1);
+		test_pattern_buffer,
+		test_pattern_size);
 }
 
 static void dp_test_send_link_test_pattern(struct dc_link *link)