usb: xhci: Set bulk EP maxpacket to 8 for buggy FS devices

Some FS devices report maxpacket size as 4 for their BULK EPs
which is incorrect as per USB specification. This results in
ep_config command to controller timing out and enumeration fails.
As minimum maxpacket size for FS is 8, override the same for such
devices.

CRs-fixed: 1002876
Change-Id: I70c2210b4eb93f557eef306fcbc11308b7b33e07
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>