ci: build kernels!

Change for v6.4:
 - rename sc7180-trogdor-kingoftown-r1 to sc7180-trogdor-kingoftown
 - enable BCM2835 on ARM64 (Raspberry Pi) thx @ Eric
Change for v6.6:
 - source symlink in modules directory no longer exists

Signed-off-by: David Heidelberg <david@ixit.cz>