The usb-kbd key repeat code assumes that reports get repeated every 40 ms,
this is never true when using CONFIG_SYS_USB_EVENT_POLL_VIA_CONTROL_EP, and
does not always works for CONFIG_SYS_USB_EVENT_POLL and
CONFIG_SYS_USB_EVENT_POLL_VIA_INT_QUEUE since not all usb keyboards honor
the usb_set_idle() command.

For CONFIG_SYS_USB_EVENT_POLL we must use usb_set_idle() since we do a
blocking wait for the hid report, so if we do not tell the keyboard to send
a hid report every 40ms even if nothing changes then we will block u-boot
for 1s (the default u-boot usb interrupt packet timeout). Note that in this
case on keyboards which do not support usb_set_idle() we loose and we actually
get 1s latencies on other u-boot activities.

For the other poll-methods this commit stops using usb_set_idle() and instead
repeats the last received hid-report every 40 ms as long as no new hid-report
is received. This fixes key-repeat not working at all with
CONFIG_SYS_USB_EVENT_POLL_VIA_CONTROL_EP and fixes it not working with
keyboards which do not implement usb_set_idle() when using
CONFIG_SYS_USB_EVENT_POLL_VIA_INT_QUEUE.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>