x86/Kconfig: Simplify NR_CPUS config

Clean up and simplify the X86 NR_CPUS Kconfig symbol/option by
introducing RANGE_BEGIN_CPUS, RANGE_END_CPUS, and DEF_CONFIG_CPUS.
Then combine some default values when their conditionals can be
reduced.

Also move the X86_BIGSMP kconfig option inside an "if X86_32"/"endif"
config block and drop its explicit "depends on X86_32".

Combine the max. 8192 cases of RANGE_END_CPUS (X86_64 only).
Split RANGE_END_CPUS and DEF_CONFIG_CPUS into separate cases for
X86_32 and X86_64.

Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/0b833246-ed4b-e451-c426-c4464725be92@infradead.org


Link: lkml.kernel.org/r/CA+55aFzOd3j6ZUSkEwTdk85qtt1JywOtm3ZAb-qAvt8_hJ6D4A@mail.gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>