LE Audio: Add `bt_audio_get_chan_count`

[Thalley]

Is your enhancement proposal related to a problem? Please describe.
In LE audio, the channel or location values (enum bt_audio_location) are bitfields.
When decoding an SDU, which may have multiple frames per frame block, it's a good idea for the receiver to verify the frame block to see if it matches the number of channels for the stream.

Describe the solution you'd like
Implement a function bt_audio_get_chan_count that takes an enum bt_audio_location and returns the number of channels in that value.

The implementation would be something like

uint8_t bt_audio_get_chan_count(enum bt_audio_location chan_allocation)
{
	uint8_t cnt = 0U;

	if (chan_allocation == BT_AUDIO_LOCATION_MONO_AUDIO) {
		return 1;
	}

	while (chan_allocation != 0) {
		cnt += chan_allocation & 1U;
		chan_allocation >>= 1;
	}

	return cnt;
}

Describe alternatives you've considered
N/A

Additional context
N/A

[ajf58]

Would using POPCOUNT[1] instead of the while loop be sufficient here?

[1] https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/toolchain/gcc.h#L267

[Thalley]

Would using POPCOUNT[1] instead of the while loop be sufficient here?

[1] https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/toolchain/gcc.h#L267

That is a good suggestion!
If it works on multiple toolchains and not just GCC, then yes - At least it can replace the loop, but we still need the

	if (chan_allocation == BT_AUDIO_LOCATION_MONO_AUDIO) {
		return 1;
	}

[babrsn]

assign to @bbaa-demant