usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler

The dummy_hcd transfer scheduler assumes that the internal kernel timer
frequency is set to 1000Hz to give a polling interval of 1ms. Reducing
the timer frequency will result in an anti-proportional reduction in
transfer performance. Switch to a hrtimer to decouple this association.

Signed-off-by: Marcello Sylvester Bauer <marcello.bauer@9elements.com>
Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/57a1c2180ff74661600e010c234d1dbaba1d0d46.1712843963.git.sylv@sylv.io


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>