Xenomai 3: enable additional Xenomai features and tweak CPU config for better latency response

[leograba]

After the initial support of Xenomai 3, some additional config that may be useful for customers on a reference image are included.

Some kernel config affect the latency of Xenomai. This commit fine-tune some of these config so the CPU avoid context switching when idle, and reduce the frequency of switching.

[microhobby]

LGTM