drivers: net: xgene: Remove acpi_has_method() calls

acpi_evaluate_object will already return an error if the needed method
does not exist. Remove unnecessary acpi_has_method() calls and check the
returned acpi_status for failure instead.

Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>