spi: fix build break in spi-fsl-espi.c

Fix a build error introduced by 24778be2 "spi: convert drivers to use
bits_per_word_mask":

drivers/spi/spi-fsl-espi.c:162:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '->' token

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>