[usb] Reset control endpoints immediately after failure

[usb] Reset control endpoints immediately after failure

The current error handling mechanism defers the endpoint reset until
the next use of the endpoint, on the basis that errors are detected
during completions and completion handling should not recursively call
usb_poll().

In the case of usb_control(), we are already at the level that calls
usb_poll() and can therefore safely perform the endpoint reset
immediately.  This has no impact on functionality, but does make
debugging traces easier to read since the reset will appear
immediately after the causative error.

Signed-off-by: Michael Brown <mcb30@ipxe.org>