buildroot

linux-firmware: drop revision handling for iwlwifi

This avoids a lot of unnecessary complication with lots of revison
knobs for different chipsets and it's consequence when bumping
linux-firmware as well.

Users can purge unwanted versions from a post processing script if
target space is too constrained.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>