Platform/RPi3: Reduce debug noise when using a USB network device

The design of the EFI_USB2_HC_PROTOCOL does not allow for long-lived
bulk IN transactions as used by network devices, but instead requires
the network driver to rely on repeatedly issuing bulk IN transactions
with a very short timeout and in the expectation that most bulk IN
transactions will time out since no packet will have been received.

Timeouts are therefore normal and expected events when using a USB
network device under UEFI.  This currently results in a constant
stream of spurious "Wait4Bit: set timeout" and "Channel %u did not
halt" debug messages whenever the network device is open.

All callers of Wait4Bit already report a meaningful error in the event
of a timeout, so the Wait4Bit message may safely be removed without
impacting the ability to debug the code.

The "Channel %u did not halt" message may be moved to its sole call
site and restricted to the situation in which the subsequent attempt
to gracefully disable the channel did actually fail.

Signed-off-by: Pete Batard <pete@akeo.ie>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>