When I created wait_for_chhltd(), I noticed that some instances of the
code it replaced expected the ACK bit to be set and others didn't. I
assumed this was an accidental inconsistency in the code, so wrote
wait_for_chhltd() to always expect ACK to be set. This code appeared to
work correctly for both enumeration of USB keyboards and operation of
USB Ethernet devices. However, this change broke USB Mass Storage (at
least my USB SD card reader). This change reverts to exactly the
original behaviour. I'm not sure why the ACK bit isn't always set
(perhaps a quirk in the USB HW or DWC2 controller), but the code works
this way!

Fixes: 5be4ca7d6ac8 ("usb: dwc2: unify waiting for transfer completion")
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>