ethernet: sun: add check for the mdesc_grab()

stable inclusion
from stable-v5.10.176
commit d4dbd26f985c1cb9a36610708beb01cf0ed95741
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8CHVQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d4dbd26f985c1cb9a36610708beb01cf0ed95741



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[ Upstream commit 90de546d ]

In vnet_port_probe() and vsw_port_probe(), we should
check the return value of mdesc_grab() as it may
return NULL which can caused NPD bugs.

Fixes: 5d01fa0c ("ldmvsw: Add ldmvsw.c driver code")
Fixes: 43fdf274 ("[SPARC64]: Abstract out mdesc accesses for better MD update handling.")
Signed-off-by: Liang He <windhl@126.com>
Reviewed-by: Piotr Raczynski <piotr.raczynski@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>