mb/google/guybrush: Document USB mapping in devicetree

Add a short documenting comment to each usb entry in devicetree so it is
clear which function each usb port maps to.

BUG=None
TEST=Build
BRANCH=None

Change-Id: I14cbb6af021bb27c89aa82456722f21aa09617be
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56725
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb b/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb
index 8629a64..edd0a02 100644
--- a/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb
+++ b/src/mainboard/google/guybrush/variants/baseboard/devicetree.cb
@@ -93,6 +93,7 @@
 
 	register "usb_phy_custom" = "1"
 	register "usb_phy" = "{
+		/* Left USB C0 Port */
 		.Usb2PhyPort[0] = {
 			.compdstune = 3,
 			.sqrxtune = 3,
@@ -104,6 +105,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 1,
 		},
+		/* Left USB A0 Port or WWAN */
 		.Usb2PhyPort[1] = {
 			.compdstune = 3,
 			.sqrxtune = 3,
@@ -115,6 +117,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 1,
 		},
+		/* User facing camera */
 		.Usb2PhyPort[2] = {
 			.compdstune = 1,
 			.sqrxtune = 3,
@@ -126,6 +129,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 2,
 		},
+		/* World facing camera */
 		.Usb2PhyPort[3] = {
 			.compdstune = 1,
 			.sqrxtune = 3,
@@ -137,6 +141,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 2,
 		},
+		/* Right USB C1 Port */
 		.Usb2PhyPort[4] = {
 			.compdstune = 3,
 			.sqrxtune = 3,
@@ -148,6 +153,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 1,
 		},
+		/* Right USB A1 Port */
 		.Usb2PhyPort[5] = {
 			.compdstune = 5,
 			.sqrxtune = 3,
@@ -159,6 +165,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 1,
 		},
+		/* WiFi / Bluetooth */
 		.Usb2PhyPort[6] = {
 			.compdstune = 1,
 			.sqrxtune = 3,
@@ -170,6 +177,7 @@
 			.txhsxvtune = 3,
 			.txrestune = 2,
 		},
+		/* Smart Card */
 		.Usb2PhyPort[7] = {
 			.compdstune = 1,
 			.sqrxtune = 3,
@@ -181,25 +189,28 @@
 			.txhsxvtune = 3,
 			.txrestune = 2,
 		},
-
+		/* Left USB C0 Port */
 		.Usb3PhyPort[0] = {
 			.tx_term_ctrl=2,
 			.rx_term_ctrl=2,
 			.tx_vboost_lvl_en=1,
 			.tx_vboost_lvl=5,
 		},
+		/* Left USB A0 Port or WWAN */
 		.Usb3PhyPort[1] = {
 			.tx_term_ctrl=2,
 			.rx_term_ctrl=2,
 			.tx_vboost_lvl_en=1,
 			.tx_vboost_lvl=5,
 		},
+		/* Right USB C1 Port */
 		.Usb3PhyPort[2] = {
 			.tx_term_ctrl=2,
 			.rx_term_ctrl=2,
 			.tx_vboost_lvl_en=1,
 			.tx_vboost_lvl=5,
 		},
+		/* Right USB A1 Port */
 		.Usb3PhyPort[3] = {
 			.tx_term_ctrl=2,
 			.rx_term_ctrl=2,