xhci(4): Ensure the so-called data toggle gets properly reset.

xhci(4): Ensure the so-called data toggle gets properly reset.

Use the drop and enable endpoint context commands to force a reset of
the data toggle for USB 2.0 and USB 3.0 after:
 - clear endpoint halt command (when the driver wishes).
 - set config command (when the kernel or user-space wants).
 - set alternate setting command (only affected endpoints).

Some XHCI HW implementations may not allow the endpoint reset command when
the endpoint context is not in the halted state.

Reported by:		Juniper and Gary Jennejohn
MFC after:		1 week
Sponsored by:		NVIDIA Networking