A static analysis tool called BEAM detected possible side effect from
assert() calling a helper which may change an XHCI ring after every call.
This moves xhci_ring_fetch() out of assert() so it will be called
with and without enabled debug.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-id: 1468812548-31868-1-git-send-email-aik@ozlabs.ru
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>