include/linux/bcd.h: remove comments

- the macros are gone
- there's no more code in this file,
  LGPL + GPL = GPL,
  and the code that was moved to lib/bcd.c is anyway trivial

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>