package/xenomai: disable for cortex-M cpus
Following include/asm-arm/features.h, Xenomai doesn't support cortex-M
cpus.
error "Could not find current ARM architecture"
Fixes:
http://autobuild.buildroot.net/results/06a/06a52b2c2c23df595f58feb6b95437fc65a86d31
Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>