usb: device: fix control endpoint handling with MPS of 8 bytes

The possible control endpoint MPS for USB 2.0 FS devices is
8, 16, 32, or 64 bytes. Typically, USB2.0 compliant devices support MPS
up to 64 bytes, and we have not had the need to support other MPS.

This patch implements a mechanism to fall back to the minimum allowed
MPS when a controller is likely a USB 1.1 compliant device and does
not support control endpoint MPS of 64 bytes.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>