commit c561a575 upstream.

BugLink: https://bugs.launchpad.net/bugs/1400215

ath3k devices fail to load firmwares on xHCI buses, but work well on
EHCI, this might be a compatibility issue between xHCI and ath3k chips.
As my testing result, those chips will work on xHCI buses again with
this patch.

This workaround is from Qualcomm, they also did some workarounds in
Windows driver.
Signed-off-by: Adam Lee <adam.lee@canonical.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>