drivers/rtc/rtc-tps65910.c: fix incorrect return value on error

'ret' was not initialized to correct error value before returning.
Since 'irq' is also being tested for 0, we cannot return irq itself as
it means function is success even though we are returning before
completing the probe.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Venu Byravarasu <vbyravarasu@nvidia.com>
Cc: Chiwoong Byun <woong.byun@samsung.com>
Cc: Jonghwa Lee <jonghwa3.lee@samsung.com>
Cc: Laxman dewangan <ldewangan@nvidia.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>