rtc: rtc-s35390a.c needs the bitreverse library

rtc-s35390a uses BITREVERSE functions so it needs to select that config symbol
to ensure that the functions are built.

  drivers/built-in.o: In function `s35390a_set_datetime':
  linux-2.6.25-rc8-git7/drivers/rtc/rtc-s35390a.c:144: undefined reference to `byte_rev_table'
  drivers/built-in.o: In function `s35390a_get_datetime':
  linux-2.6.25-rc8-git7/drivers/rtc/rtc-s35390a.c:163: undefined reference to `byte_rev_table'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>