[PATCH 0/2 F][SRU][oem-5.6][L-R-M] Add the NVIDIA 455 series

[Alberto Milone]

Add the NVIDIA 455 driver.

Also, provide a new virtual package, so that packagers
can specify a dependency on signed modules (as opposed to
the DKMS packages).

This will require updating the dkms-versions file when
cranking.

BugLink: https://bugs.launchpad.net/bugs/1902093

Signed-off-by: Alberto Milone <alberto.milone at canonical.com>

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