Update firmware-update.md

Explained the order of firmware flashing and noted the requirement of
network boot enabled.

Signed-off-by: Maciej Pijanowski <[email protected]>

Author: wessel-novacustom

docs/unified/novacustom/firmware-update.md

@@ -90,4 +90,8 @@ Follow the manual update procedure described in the [DTS firmware update
 documentation](https://docs.dasharo.com/dasharo-tools-suite/documentation/#local-firmware-update).
 
 > Please make sure you that you update the BIOS firmware and the EC firmware
-> respectively.
+> respectively, as the laptop will power off after the EC firmware flash.
+>
+> Please also note that
+> [network boot must be enabled](https://docs.dasharo.com/dasharo-menu-docs/dasharo-system-features/#networking-options)
+> if you want to boot to the Dasharo Tools Suite over a network connection.