feat(usb): add ESP32-S31 DWC/UTMI support

Add ESP32-S31 USB DWC/UTMI LL headers, SoC register structures, peripheral
descriptors, capabilities, and linker mappings so the HS OTG controller and
UTMI PHY can be built in esp_hal_usb.

Introduce SOC_USB_FSLS_PHY_NUM on USB-OTG targets to separate FSLS USB_WRAP
support from OTG/UTMI support. Use it to gate usb_wrap, the USB PHY driver,
docs, and example build rules on targets without an FSLS PHY.

Also add UTMI data pulldown control to the HAL, clear the boot-time DWC
suspend state on ESP32-S31, alias the legacy internal PHY target to UTMI for
backward compatibility, and extend usb_phy tests for UTMI-only targets.

components/esp_hal_usb/esp32p4/include/hal/usb_utmi_ll.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -12,6 +12,10 @@
 #include "soc/hp_sys_clkrst_struct.h"
 #include "soc/hp_system_struct.h"
 #include "soc/usb_utmi_struct.h"
+#include "hal/config.h"
+#if HAL_CONFIG(CHIP_SUPPORT_MIN_REV) >= 300
+#include "soc/lp_system_struct.h"
+#endif
 
 #ifdef __cplusplus
 extern "C" {
@@ -81,6 +85,29 @@ FORCE_INLINE_ATTR void _usb_utmi_ll_reset_register(void)
         _usb_utmi_ll_reset_register(__VA_ARGS__); \
     } while(0)
 
+/**
+ * @brief Enable/disable 15k pulldown resistors on D+/D- lines
+ *
+ * In USB Host mode, 15k pulldown resistors must be connected on both D+ and D-.
+ * In USB Device mode, pulldown resistors must be disconnected.
+ *
+ * @note On ESP32-P4 v3+, pulldowns are no longer controlled by USB-OTG peripheral
+ *       and must be controlled by software via LP_SYS registers.
+ *       On earlier revisions, pulldowns are controlled by USB-OTG hardware.
+ *
+ * @param[in] enable true to connect pulldowns (Host mode), false to disconnect (Device mode)
+ */
+FORCE_INLINE_ATTR void usb_utmi_ll_enable_data_pulldowns(bool enable)
+{
+#if HAL_CONFIG(CHIP_SUPPORT_MIN_REV) >= 300
+    LP_SYS.hp_usb_otghs_phy_ctrl.hp_utmiotg_dppulldown = enable;
+    LP_SYS.hp_usb_otghs_phy_ctrl.hp_utmiotg_dmpulldown = enable;
+#else
+    // On pre-v3 ESP32-P4, pulldowns are controlled by the USB-OTG peripheral
+    (void)enable;
+#endif
+}
+
 /**
  * @brief Enable precise detection of VBUS
  *