fpga: machxo2-spi: Return an error on failure

stable inclusion
from stable-5.10.70
commit 5c6bfde245d82a5ccd27d7f4a720d8222ba943ee
bugzilla: 182949 https://gitee.com/openeuler/kernel/issues/I4I3GQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c6bfde245d82a5ccd27d7f4a720d8222ba943ee



--------------------------------

[ Upstream commit 34331739 ]

Earlier successes leave 'ret' in a non error state, so these errors are
not reported. Set ret to -EINVAL before going to the error handler.

This addresses two issues reported by smatch:
drivers/fpga/machxo2-spi.c:229 machxo2_write_init()
  warn: missing error code 'ret'

drivers/fpga/machxo2-spi.c:316 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: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tom Rix <trix@redhat.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>