spi: fsl-cpm: Correct the free:ing

The fsl_spi_cpm_free() function does not make the same
checks as the error path in fsl_spi_cpm_init() leading
to crashes on error.

Cc: Fabio Estevam <festevam@gmail.com>
Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20191113014442.12100-1-linus.walleij@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>