drivers/intel/usb4: Add driver for USB4 retimer device

The USB4 retimer device needs to declare a _DSM with specific functions
that allow for GPIO control to turn off the power when an external
device is not connected.  This driver allows the mainboard to provide
the GPIO that is connected to the power control.

BUG=b:156957424

Change-Id: Icfb85dc3c0885d828aba3855a66109043250ab86
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44918
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile.inc b/Makefile.inc
index 882673b..297f7b1 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -80,7 +80,7 @@
 subdirs-y += src/ec/acpi $(wildcard src/ec/*/*) $(wildcard src/southbridge/*/*)
 subdirs-y += $(wildcard src/soc/*/*) $(wildcard src/northbridge/*/*)
 subdirs-y += src/superio
-subdirs-y += $(wildcard src/drivers/*) $(wildcard src/drivers/*/*)
+subdirs-y += $(wildcard src/drivers/*) $(wildcard src/drivers/*/*) $(wildcard src/drivers/*/*/*)
 subdirs-y += src/cpu src/vendorcode
 subdirs-y += util/cbfstool util/sconfig util/nvramtool util/pgtblgen util/amdfwtool
 subdirs-y += util/futility util/marvell util/bincfg util/supermicro