Upstream added a standalone SPI kernel-loader which fixes the unbootable
image for the WDR4900. Thus, we can re-introduce this device to Gluon.

Signed-off-by: David Bauer <mail@david-bauer.net>

Remove support for the TP-Link WDR4900, as it us currently unable to
load its kernel sure to factory bootloader constraints.

Progress on this topic is tracked in #2491

This adds support for the Sophos RED 15w rev.1 gateway.

It is a branch-office SD-WAN device based on the P1014 networking SoC.

Signed-off-by: David Bauer <mail@david-bauer.net>