package/linux-firmware: add option for iwl7265 firmware

New firmware to support iwlwifi-7265. Only comes in rev-8 or rev-9
flavours, so hide rev-7 when iwlwifi-7265 is selected.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>