qca: update bluetooth firmware for QCA6174

Bugfixes for QCA6174.

While at it, to avoid confusion, also change the name of driver to
'btqca' in WHENCE file because that's what it is called in kernel images
(drivers/bluetooth/btqca.ko). Of course we cannot change the name of
directory 'qca' and that has to remain forever, but better to fix the
documentation to make it clear what driver this is.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>