drivers: net: xgene: Remove unnecessary forward declarations

drivers: net: xgene: Remove unnecessary forward declarations

Clang warns:

drivers/net/ethernet/apm/xgene/xgene_enet_main.c:33:36: warning:
tentative array definition assumed to have one element
static const struct acpi_device_id xgene_enet_acpi_match[];
                                   ^
1 warning generated.

Both xgene_enet_acpi_match and xgene_enet_of_match are defined before
their uses at the bottom of the file so this is unnecessary. When
CONFIG_ACPI is disabled, ACPI_PTR becomes NULL so xgene_enet_acpi_match
doesn't need to be defined.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>