spi: checking for NULL instead of IS_ERR

spi_replace_transfers() returns error pointers on error, it never
returns NULL.

Fixes: d9f121227281 ('spi: core: add spi_split_transfers_maxsize')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
1 file changed