The target uses 5.4 as default kernel since 04/2020.
Kernel 4.19 support is not really maintained anymore, and there has
been a lot of changes between 4.19 and 5.4 on this target. Despite,
new devices are typically added for 5.4 only anyway.
Thus, make maintaining of old stuff and reviewing of new stuff
easier by removing support for kernel 4.19.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
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