The Meraki MR74 is part of the "Insect" series. This device is
essentially an outdoor variant of the MR33 with identical hardware, but
requiring a config@3 DTS option to be set to allow booting with the
stock u-boot.
The install procedure is replicated from the MR33, with the exception
being that the MR74 sysupgrade image must be used.
Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
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