Add missing capability bit for CDC ACM serial break support

The send break capability bit is needed for serial break support with Linux and possibly MacOS hosts. [A recent Linux kernel patch made it check the ACM capability bits before sending a serial break](raspberrypi/linux@19e321c).

Author: trejan

src/device/usbd.h

@@ -221,8 +221,8 @@ TU_ATTR_WEAK bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb
   5, TUSB_DESC_CS_INTERFACE, CDC_FUNC_DESC_HEADER, U16_TO_U8S_LE(0x0120),\
   /* CDC Call */\
   5, TUSB_DESC_CS_INTERFACE, CDC_FUNC_DESC_CALL_MANAGEMENT, 0, (uint8_t)((_itfnum) + 1),\
-  /* CDC ACM: support line request */\
-  4, TUSB_DESC_CS_INTERFACE, CDC_FUNC_DESC_ABSTRACT_CONTROL_MANAGEMENT, 2,\
+  /* CDC ACM: support line request + send break */\
+  4, TUSB_DESC_CS_INTERFACE, CDC_FUNC_DESC_ABSTRACT_CONTROL_MANAGEMENT, 6,\
   /* CDC Union */\
   5, TUSB_DESC_CS_INTERFACE, CDC_FUNC_DESC_UNION, _itfnum, (uint8_t)((_itfnum) + 1),\
   /* Endpoint Notification */\