spi: spi-bcm-qspi: style: Simplify bool comparison

Fix the following coccicheck warning:
./drivers/spi/spi-bcm-qspi.c:884:5-34: WARNING: Comparison to bool

Signed-off-by: YANG LI <abaci-bugfix@linux.alibaba.com>
Reported-by: Abaci <Robot&lt;abaci@linux.alibaba.com>
Link: https://lore.kernel.org/r/1610357189-60031-1-git-send-email-abaci-bugfix@linux.alibaba.com


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