mb/google/volteer/eldrid: Use #define symbols for usb2_ports config

It's easier to understand what these symbolic names mean rather than
using the constants; the static.c will will end up (indirectly)
including `soc/usb.h` therefore the macros are in scope here.

Change-Id: I5ef977a05a2522e177f32c99bfab74f9288ae869
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49488
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nick Chen <nick_xr_chen@wistron.corp-partner.google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/mainboard/google/volteer/variants/eldrid/overridetree.cb

@@ -79,10 +79,11 @@ chip soc/intel/tigerlake
 	#lower camera driving
 	register "usb2_ports[4]" = "{
 		.enable = 1,
-		.tx_bias = 0,
-		.tx_emp_enable = 0,
-		.pre_emp_bias = 0,
-		.pre_emp_bit = 0,
+		.ocpin = OC_SKIP,
+		.tx_bias = USB2_BIAS_0MV,
+		.tx_emp_enable = USB2_EMP_OFF,
+		.pre_emp_bias = USB2_BIAS_0MV,
+		.pre_emp_bit = USB2_FULL_BIT_PRE_EMP,
 	}"
 
 	#Type-A / Type-C C0