xfrm: Allow transport-mode states with AF_UNSPEC selector

stable inclusion
from stable-v5.10.176
commit 0da0b816972a88dc82431586cb2c1e85876f9c77
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I87BGI

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0da0b816972a88dc82431586cb2c1e85876f9c77



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[ Upstream commit c276a706 ]

xfrm state selectors are matched against the inner-most flow
which can be of any address family.  Therefore middle states
in nested configurations need to carry a wildcard selector in
order to work at all.

However, this is currently forbidden for transport-mode states.

Fix this by removing the unnecessary check.

Fixes: 13996378 ("[IPSEC]: Rename mode to outer_mode and add inner_mode")
Reported-by: David George <David.George@sophos.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>