board: st: move type-c stusb1600 controller code in a driver

Migrate the ST Microelectronics STUSB160X Type-C controller code in
a generic I2C driver in st/common, based on Linux one in :
drivers/usb/typec/stusb160x.c

This patch simplifies the stm32mp1 board code and allows to reuse
this STUSB160X driver in other boards.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/board/st/common/stusb160x.h b/board/st/common/stusb160x.h
new file mode 100644
index 0000000..fe39840
--- /dev/null
+++ b/board/st/common/stusb160x.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020, STMicroelectronics
+ */
+
+#ifdef CONFIG_TYPEC_STUSB160X
+int stusb160x_cable_connected(void);
+#else
+int stusb160x_cable_connected(void) { return -ENODEV; }
+#endif