kconfig: print the range of integer/hex symbol in help text

Without this patch, one has to refer to the Kconfig file to find
out the range of an integer/hex symbol.

  │ Symbol: NR_CPUS [=4]
  │ Type  : integer
  │ Range : [2 8]
  │ Prompt: Maximum number of CPUs
  │   Defined at arch/x86/Kconfig:761
  │   Depends on: SMP [=y] && !MAXSMP [=n]
  │   Location:
  │     -> Processor type and features

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>