drivers/rtc/rtc-tps65910.c: rename irq to match device

A cosmetic change to rename the irq name to match the device name.

Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
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>