ACPI: scan: Use the acpi_device_is_present() helper in more places

acpi_device_is_present() checks the present or functional bits
from the cached copy of _STA.

A few places open-code this check. Use the helper instead to
improve readability.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Miguel Luis <miguel.luis@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>