kconfig: print symbol type in help text

Randy suggested to print out the symbol type in gconfig.

Note this change does more than Randy's suggestion, that it also
affects menuconfig and "make config".

  │ Symbol: BLOCK [=y]
  │ Type  : boolean
  │ Prompt: Enable the block layer
  │   Defined at block/Kconfig:4
  │   Depends on: EMBEDDED [=n]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>