fpga: machxo2-spi: Fix missing error code in machxo2_write_complete()

stable inclusion
from stable-5.10.70
commit c6ecdcba9da3416030cfc9376dce83ec0d21cef0
bugzilla: 182949 https://gitee.com/openeuler/kernel/issues/I4I3GQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6ecdcba9da3416030cfc9376dce83ec0d21cef0



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[ Upstream commit a1e44708 ]

The error code is missing in this code scenario, add the error code
'-EINVAL' to the return value 'ret'.

Eliminate the follow smatch warning:

drivers/fpga/machxo2-spi.c:341 machxo2_write_complete()
  warn: missing error code 'ret'.

[mdf@kernel.org: Reworded commit message]
Fixes: 88fb3a00 ("fpga: lattice machxo2: Add Lattice MachXO2 support")
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>