pcb: replace USB PD interrupt pin with a VBUS voltage sense

The PD interrupt is not useful, and we need the pin for VBUS voltage drop
detection.

pcb/lib/mainboard.kicad_sym

@@ -5188,6 +5188,124 @@
 		)
 		(embedded_fonts no)
 	)
+	(symbol "HT70XXA-1"
+		(exclude_from_sim no)
+		(in_bom yes)
+		(on_board yes)
+		(property "Reference" "U"
+			(at 5.588 7.874 0)
+			(effects
+				(font
+					(size 1.27 1.27)
+				)
+			)
+		)
+		(property "Value" "HT70XXA-1"
+			(at -6.604 7.874 0)
+			(effects
+				(font
+					(size 1.27 1.27)
+				)
+			)
+		)
+		(property "Footprint" "Package_TO_SOT_SMD:SOT-89-3"
+			(at 8.89 -1.27 0)
+			(effects
+				(font
+					(size 1.27 1.27)
+				)
+				(hide yes)
+			)
+		)
+		(property "Datasheet" "https://www.holtek.com/webapi/116711/HT70xxA-1v261.pdf"
+			(at 8.89 -1.27 0)
+			(effects
+				(font
+					(size 1.27 1.27)
+				)
+				(hide yes)
+			)
+		)
+		(property "Description" "Low power voltage detector"
+			(at 8.89 -1.27 0)
+			(effects
+				(font
+					(size 1.27 1.27)
+				)
+				(hide yes)
+			)
+		)
+		(symbol "HT70XXA-1_0_0"
+			(pin input line
+				(at -7.62 0 0)
+				(length 2.54)
+				(name "VDD"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+				(number "2"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+			)
+			(pin power_in line
+				(at 0 -7.62 90)
+				(length 2.54)
+				(name "VSS"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+				(number "3"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+			)
+			(pin open_collector line
+				(at 7.62 0 180)
+				(length 2.54)
+				(name "OUT"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+				(number "1"
+					(effects
+						(font
+							(size 1.27 1.27)
+						)
+					)
+				)
+			)
+		)
+		(symbol "HT70XXA-1_1_1"
+			(rectangle
+				(start -5.08 5.08)
+				(end 5.08 -5.08)
+				(stroke
+					(width 0)
+					(type default)
+				)
+				(fill
+					(type background)
+				)
+			)
+		)
+		(embedded_fonts no)
+	)
 	(symbol "HUSB238A"
 		(exclude_from_sim no)
 		(in_bom yes)