s5k3l6xx: Filter out focus pixels

This is a hack, a proper solution is adding a custom control. Userpace hasn't caught up yet however.

It might be annoying when debugging, but then there's the override interface for this purpose already.
2 jobs for pureos/byzantium in 65 minutes and 20 seconds (queued for 1 second)
Status Job ID Name Coverage
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passed #357114
librem5
build:aarch64

00:34:52

passed #357115
librem5:arm64
build:deb

01:05:20