usb: gadget: remove useless parameter in alloc_ep_req()

The default_length parameter of alloc_ep_req was not really necessary
and gadget drivers would almost always create an inline function to pass
the same value to len and default_len.

This patch removes that parameter and updates all calls to alloc_ep_req() to
use the new API.

Change-Id: Idfe0e0fde8faf5f713a8368d29a4bd155208ffa2
Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Git-commit: aadbe812463f8af1751debb0eaaeec8a778d7ff1
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git


[ajaya@codeaurora.org: fix merge conflicts]
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>