ACPI / SBS: fix inconsistent indenting inside if statement

The indenting in acpi_battery_set_alarm is inconsistent and has been
so since 2007; commit 94f6c086
("ACPI: SBS: Add support for power_supply class (and sysfs)"). Minor
fix for this, no code functionality change.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>