net: pch_gbe: Remove dead RINGFREE code

The pch_gbe driver includes some code which appears to be an attempt to
work around a problem with the pch_gbe_free_rx_resources &
pch_gbe_free_tx_resources functions that no longer exists. Remove the
code guarded by the never-defined RINGFREE preprocessor macro.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Signed-off-by: David S. Miller <davem@davemloft.net>