Bluetooth: ath3k: workaround the compatibility issue with xHCI controller

Bluetooth: ath3k: workaround the compatibility issue with xHCI controller

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>