usb: ci_udc: fix request allocation when endpoints are disabled

The ci_udc driver request allocation assumes that the endpoint descriptor
pointer is set to retrieve the endpoint number, but that is only true
when the endpoint is enabled. This results in a NULL ptr dereference
which for me happens to return 0 value. This causes the EP0 request
struct to be returned for other endpoints. Some gadget drivers like
fastboot and USB MS work fine, but ethernet does not.

Really, the ci_udc driver is the oddball here doing this EP0 special
case handling Stephen added. All the other drivers alloc/free functions
are pretty much the same with the only variation being the size of the
private struct. This could all be consolidated to a common function.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Marek Vasut <marex@denx.de>
Acked-by: Stephen Warren <swarren@nvidia.com>