iavf: Fix handling of dummy receive descriptors

stable inclusion
from stable-v5.10.134
commit c6af94324911ef0846af1a5ce5e049ca736db34b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ZVR7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6af94324911ef0846af1a5ce5e049ca736db34b



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[ Upstream commit a9f49e00 ]

Fix memory leak caused by not handling dummy receive descriptor properly.
iavf_get_rx_buffer now sets the rx_buffer return value for dummy receive
descriptors. Without this patch, when the hardware writes a dummy
descriptor, iavf would not free the page allocated for the previous receive
buffer. This is an unlikely event but can still happen.

[Jesse: massaged commit message]

Fixes: efa14c39 ("iavf: allow null RX descriptors")
Signed-off-by: Przemyslaw Patynowski <przemyslawx.patynowski@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>