drivers/rtc/rtc-hym8563.c: return clock rate even when clock is disabled

When the clock is disabled, do not return a rate of 0 but instead return
the rate the clock will be running at after it gets enabled.  This
prevents problems when the core clock code is trying to determine a
suitable rate, while the clock is still off.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>