i2c: smbus: fix NULL function pointer dereference

stable inclusion
from stable-v4.19.313
commit 40f1d79f07b49c8a64a861706e5163f2db4bd95d
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9QRRJ
CVE: CVE-2024-35984

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=40f1d79f07b49c8a64a861706e5163f2db4bd95d



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[ Upstream commit 91811a31b68d3765b3065f4bb6d7d6d84a7cfc9f ]

Baruch reported an OOPS when using the designware controller as target
only. Target-only modes break the assumption of one transfer function
always being available. Fix this by always checking the pointer in
__i2c_transfer.

Reported-by: Baruch Siach <baruch@tkos.co.il>
Closes: https://lore.kernel.org/r/4269631780e5ba789cf1ae391eec1b959def7d99.1712761976.git.baruch@tkos.co.il


Fixes: 4b1acc43 ("i2c: core changes for slave support")
[wsa: dropped the simplification in core-smbus to avoid theoretical regressions]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>