rtc-pcf8563: remove client validation

Validating clients with black magic register checks doesn't make much
sense for new-style i2c driver and has been known to fail on valid NXP
pcf8563 chips.  This patch removes the client validation code.

Signed-off-by: Laurent Pinchart <laurentp@cse-semaphore.com>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>