spi: sprd: adi: Use IS_ENABLED() to validate configs

spi: sprd: adi: Use IS_ENABLED() to validate configs

If the Spreadtrum wachdog is loaded as a module, we still need set default
watchdog reboot mode in case the rebooting is caused by watchdog. But now
we can not set the watchdog reboot mode by using '#ifdef' to validate
the watchdog configuration, thus we can change to use IS_ENABLED() to
fix this issue.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/e38807eadd5550add8eb90dd3f8fbe2cfc39cc13.1586759322.git.baolin.wang7@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>