ipmi: ssif_bmc: fix missing check for copy_to_user() partial failure

ipmi: ssif_bmc: fix missing check for copy_to_user() partial failure

copy_to_user() returns the number of bytes that could not be copied,
with a non-zero value indicating a partial or complete failure. The
current code only checks for negative return values and treats all
non-negative results as success.

Treating any positive return value from copy_to_user() as
an error and returning -EFAULT.

Fixes: dd2bc5cc9e25 ("ipmi: ssif_bmc: Add SSIF BMC driver")
Signed-off-by: Jian Zhang <zhangjian.3032@bytedance.com>
Message-ID: <20260403090603.3988423-2-zhangjian.3032@bytedance.com>
Signed-off-by: Corey Minyard <corey@minyard.net>