misc: mei: client.c: fix problem of return '-EOVERFLOW' in mei_cl_write

[ Upstream commit ee623602 ]

Clang static analyzer complains that value stored to 'rets' is never
read.Let 'buf_len = -EOVERFLOW' to make sure we can return '-EOVERFLOW'.

Fixes: 8c8d964c

 ("mei: move hbuf_depth from the mei device to the hw modules")
Signed-off-by: Su Hui <suhui@nfschina.com>
Link: https://lore.kernel.org/r/20231120095523.178385-2-suhui@nfschina.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>