aiccu: not available on NIOS II

Building aiccu does not work on NIOS II due to the _gp problem, and
nobody is interested to fix it for now, so we simply disallow this
package. While we're at it, we propagate the AVR32 exclusion to the
comment.

Fixes:

  http://autobuild.buildroot.net/results/786/7864cd5789a9f9b9f0603d738f4e63822d8469dd/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>