x86, cpuid: Simplify the code in cpuid_open

Peter picked up my patch for tip/x86/cpu that removes the bkl in
cpuid_open. Ingo subsequently merged that into tip/master.

This patch folds back in tglx's 55968ede164ae523692f00717f50cd926f1382a0
to my patch that removed the bkl.

This simplifies the code, and makes it consistent with the changes to
kill the bkl in msr.c as well.

Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Kacur <jkacur@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>