linux-firmware: Move Intel AC 9260 bluetooth firmware to a separate package

In order to use Bluetooth on Intel AC 9260, we need to select
linux-firmware-ibt-misc package that brings a lot of fimw-
ares that are, in most cases, irrelevant for the used hardware.

This adds a new package linux-firmware-ibt-18 that only includes
the corresponding firmware for Intel AC 9260 bluetooth chips.

Below, the link to the commit that adds Intel AC 9260 firmwares in linux-
firmware:

https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/?h=20220610&id=97339b3a1d3bf3e4c40d679896a27a25fa83765f



Reported-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Iskander Amara <iskander.amara@theobroma-systems.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>