package/wireguard-linux-compat: bump version to 1.0.20201221

Fixes a build issue with linux-rt >= 5.4.  For details, see the
announcement:
https://lists.zx2c4.com/pipermail/wireguard/2020-December/006210.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
2 files changed