wifi: rtlwifi: fix incorrect error codes in rtl_debugfs_set_write_reg()

stable inclusion
from stable-v5.10.180
commit dc55805db254d7f9990cb5a49dd771e69e70c4ae
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8DDFN

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc55805db254d7f9990cb5a49dd771e69e70c4ae



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[ Upstream commit 5dbe1f8e ]

If there is a failure during copy_from_user or user-provided data buffer is
invalid, rtl_debugfs_set_write_reg should return negative error code instead
of a positive value count.

Fix this bug by returning correct error code. Moreover, the check of buffer
against null is removed since it will be handled by copy_from_user.

Fixes: 610247f4 ("rtlwifi: Improve debugging by using debugfs")
Signed-off-by: Wei Chen <harperchen1110@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230326054217.93492-1-harperchen1110@gmail.com


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>