This commit fixes a number of issues with the reset sequence of musb-new
in host mode:

1) Our usb device probe relies on a second device reset being done after the
first descriptors read. Factor the musb reset code into a usb_reset_root_port
function (and add this as an empty define for other controllers), and call
this when a device has no parent.

2) Just like with normal usb controllers there needs to be a delay after
reset, for normal usb controllers, this is handled in hub_port_reset, add a
delay to usb_reset_root_port.

3) Sync the musb reset sequence with the upstream kernel, clear all bits of
power except bits 4-7, and increase the time reset is asserted to 50 ms.

With these fixes an usb keyboard I have now always enumerates properly, where
as earlier it would only enumerare properly once every 5 tries.

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