serial: 8250_dw: Switch to use acpi_dev_present()

Special settings for APMC0D08 are applied when device is present
in the system. To check its presence we may use acpi_dev_present()
instead of current open coded variant.

Cc: Feng Kan <fkan@apm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>