spi: sg2044-nor: fix signedness bug in sg2044_spifmc_write()

spi: sg2044-nor: fix signedness bug in sg2044_spifmc_write()

The "ret" variable needs to be signed for the error handling to work.
It should be type int, since it only holds zero and negative error
codes.

Fixes: de16c322eefb ("spi: sophgo: add SG2044 SPI NOR controller driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://patch.msgid.link/4e16e1bf-e5fb-4771-bc92-c5cba9aac473@stanley.mountain
Signed-off-by: Mark Brown <broonie@kernel.org>