usb_audio: Correct mixup between Input terminals and Input streams.

An "Input" terminal in USB audio terms refers to any stream of audio
going "in" to the USB device, whether that be from the outside world
(e.g. a line in jack) or from the computer (e.g. via USB OUT endpoints.)

So we cannot rely on the terminal type to tell us whether it is an in
or an out for our purposes, we have to check the stream type, and then
use that to declare to multi_audio what kind of stream we have.

Fixes USB audio mixing up inputs and outputs, especially on devices
that only have one or the other and not both. (QEMU manifested
this problem.)

usb_audio: Code cleanup.

No functional changes intended.

audio/usb: Fix for condition

Pointed out by cppcheck.

Change-Id: Ief24915908bbab41955924279847ba56faa12b09
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3506
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

usb_audio: Trim trailing spaces; change device basename to "hmulti/usb".

Everything: Update lots of code to use B_COUNT_OF macro

* Likely not everything, but the obvious uses of B_COUNT_OF

usb_audio:fix parameters web compilation logic

* parameters web compilation improved - harvest the feature units
assigned to non-streaming output terminals in the same way as ones
assigned to streaming output terminals.

Fixes #9950

USB audio/SiS7018: Set controls_count on list mix ioctl

Looks like it works with default controls count 128 on default Haiku
builds but force media-addons-server to crash in case KDEBUG_LEVEL is set
to 0. Thanks to Vitaly Diger for pointing out and testing this issue.

Rename driver folder 'usb_audio' to 'usb'

... just because the source path ./kernel/drivers/audio/usb obviously
references audio hardware so "_audio" suffix is excessive.

No functional changes.

Everything: Update lots of code to use B_COUNT_OF macro

* Likely not everything, but the obvious uses of B_COUNT_OF

usb_audio:fix parameters web compilation logic

* parameters web compilation improved - harvest the feature units
assigned to non-streaming output terminals in the same way as ones
assigned to streaming output terminals.

Fixes #9950

USB audio/SiS7018: Set controls_count on list mix ioctl

Looks like it works with default controls count 128 on default Haiku
builds but force media-addons-server to crash in case KDEBUG_LEVEL is set
to 0. Thanks to Vitaly Diger for pointing out and testing this issue.

Rename driver folder 'usb_audio' to 'usb'

... just because the source path ./kernel/drivers/audio/usb obviously
references audio hardware so "_audio" suffix is excessive.

No functional changes.