airoha: add the capability to read firmware names from dts

airoha: add the capability to read firmware names from dts

Introduce the capability to read the firmware binary names from device-tree
using the firmware-name property if available.
This is a preliminary patch to enable NPU offloading for MT7996 (Eagle)
chipset since it requires a different binary with respect to the one
used for MT7992 on the EN7581 SoC.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://github.com/openwrt/openwrt/pull/22289
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>