x86/cpuidle: publish new states only after fully initializing them

x86/cpuidle: publish new states only after fully initializing them

Since state information coming from Dom0 can arrive at any time, on
any CPU, we ought to make sure that a new state is fully initialized
before the target CPU might be using it.

Once touching that code, also do minor cleanup: A missing (but benign)
"break" and some white space adjustments.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Liu Jinsong <jinsong.liu@intel.com>