usb: gadget: change len to size_t on alloc_ep_req()

usb: gadget: change len to size_t on alloc_ep_req()

[ Upstream commit 69bb99738b5c6d56d2b1a75db9cbb4d187453c1a ]

Length of buffers should be of type size_t whenever possible. Altough
recommended, this change has no real practical change, unless a driver has a
uses a huge or negative buffer size - it might help find these bugs.

Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>