rpi-kernel: update to 4.19.81.
rpi-kernel: update to 4.19.81.

[ci skip]

- Built on armv6l, armv7l, aarch64.
- Tested on armv6l, armv7l, aarch64

Closes: #16049 [via git-merge-pr]

necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages