x86/smpboot: Re-enable init_udelay=0 by default on modern CPUs

x86/smpboot: Re-enable init_udelay=0 by default on modern CPUs

Fix a Linux-4.3 corner case performance regression, introduced by commit:

  f1ccd249319e ("x86/smpboot: Fix cpu_init_udelay=10000 corner case boot parameter misbehavior")

which allowed the cmdline  "cpu_init_udelay=" to work with all values,
including the default of 10000.

But in setting the default of 10000, it over-rode the code stat sets
the delay 0 on modern processors.

Also, tidy up use of INT/UINT.

Reported-by: Shane <shrybman@teksavvy.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dparsons@brightdsl.net
Link: http://lkml.kernel.org/r/9082eb809ef40dad02db714759c7aaf618c518d4.1448232494.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>