usb:diag:revert the f_diag update from qcom for moto tty_diag driver

Qcom update the f_diag in sm2020
And break the moto tty_diag function

Change-Id: Idf943d633fca1873e86f22c1126d8ef8ada52d72
Signed-off-by: a17671 <a17671@motorola.com>
Reviewed-on: https://gerrit.mot.com/2127809
SLTApproved: Slta Waiver
SME-Granted: SME Approvals Granted
Tested-by: Jira Key
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>
Submit-Approved: Jira Key

drivers/usb/gadget/function/f_diag.c

@@ -512,7 +512,6 @@ fail:
 }
 EXPORT_SYMBOL(usb_diag_alloc_req);
 #define DWC3_MAX_REQUEST_SIZE (16 * 1024 * 1024)
-#define CI_MAX_REQUEST_SIZE   (16 * 1024)
 /**
  * usb_diag_request_size - Max request size for controller
  * @ch: Channel handler
@@ -522,16 +521,6 @@ EXPORT_SYMBOL(usb_diag_alloc_req);
  */
 int usb_diag_request_size(struct usb_diag_ch *ch)
 {
-	struct diag_context *ctxt = ch->priv_usb;
-	struct usb_composite_dev *cdev;
-
-	if (!ctxt)
-		return 0;
-
-	cdev = ctxt->cdev;
-	if (cdev->gadget->is_chipidea)
-		return CI_MAX_REQUEST_SIZE;
-
 	return DWC3_MAX_REQUEST_SIZE;
 }
 EXPORT_SYMBOL(usb_diag_request_size);