ab8500_fg: Balance IRQ enable

In case of time out error IRQ needs to be disabled
otherwise we will get unbalanced enable/disable pairs.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Rickard Andersson <rickard.andersson@stericsson.com>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>