soc/amd/picasso: Add UPD xhci0_force_gen1

Adding xhci0_force_gen1 UPD to force USB3 port to gen1.

BUG=b:156314787
BRANCH=trembyle-bringup
TEST=Build.

Cq-Depend: chrome-internal:3013435
Change-Id: Iff3746e248625c253776c3bc3946d123b0635ffe
Signed-off-by: Chris Wang <chris.wang@amd.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/+/2217662
Reviewed-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42216
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Eric Peers <epeers@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/picasso/chip.h

@@ -103,6 +103,8 @@ struct soc_amd_picasso_config {
 		SD_EMMC_EMMC_HS400,
 		SD_EMMC_EMMC_HS300,
 	} sd_emmc_config;
+
+	uint8_t xhci0_force_gen1;
 };
 
 typedef struct soc_amd_picasso_config config_t;