ipq807x: drop target

ipq807x: drop target

The target is in an incomplete state and will not receive Kernel 5.10
support, ego it should be dropped before the next release.

People are working on ipq807x with Kernel 5.15 which is only relevant
for the second next release. Once a working patchset exists the target
can be added again.

Signed-off-by: Paul Spooren <mail@aparcar.org>