ibmvnic: Clean RX pool buffers during device close

[ Upstream commit d0869c0071e40c4407d1a4d7c9497653cf47253b ]

During device close or reset, there were some cases of outstanding
RX socket buffers not being freed. Include a function similar to the
one that already exists to clean TX socket buffers in this case.

Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>