drivers/rtc/rtc-vt8500.c: convert to use devm_kzalloc

Replace the kzalloc() and kfree() calls with devm_kzalloc().

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexey Charkov <alchark@gmail.com>
Acked-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>