mb/google/zork: update USB 2.0 controller Lane Parameter for morphius

Enhance USB 2.0 SI by increasing the level of "HS DC Voltage Level"
and "Disconnect Threshold Adjustment".
COMPDISTUNE0: 0x3->0x7
TXVREFTUNE0: 0x6->0xf

BUG=b:162614573
BRANCH=zork
TEST=1. emerge-zork coreboot
     2. check U2 registers are set correctly
     3. test with servo v4 type-c, it's working expectedly.
     4. U2 SI pass

Signed-off-by: Kevin Chiu <kevin.chiu@quantatw.com>
Change-Id: I278cc0aaddbc9fce595bf57ca69ee8abfc9f5659
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46537
Reviewed-by: Rob Barnes <robbarnes@google.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/zork/variants/morphius/overridetree.cb

@@ -35,6 +35,19 @@ chip soc/amd/picasso
 		.ports.xhci0_port2 = 1, /* Left USB3A port 2 */
 	}"
 
+	# USB 2.0 strength
+	register "usb_2_port_tune_params[3]" = "{
+		.com_pds_tune = 0x07,
+		.sq_rx_tune = 0x3,
+		.tx_fsls_tune = 0x3,
+		.tx_pre_emp_amp_tune = 0x03,
+		.tx_pre_emp_pulse_tune = 0x0,
+		.tx_rise_tune = 0x1,
+		.rx_vref_tune = 0xf,
+		.tx_hsxv_tune = 0x3,
+		.tx_res_tune = 0x01,
+	}"
+
 	# Enable I2C2 for trackpad, touchscreen, pen at 400kHz
 	register "i2c[2]" = "{
 		.speed = I2C_SPEED_FAST,