i2c: spacemit: check SDA instead of SCL after bus reset

After calling spacemit_i2c_conditionally_reset_bus(),
the controller should ensure that the SDA line is release
before proceeding.

Previously, the driver checked the SCL line instead,
which does not guarantee that the bus is truly idle.

This patch changes the check to verify SDA. This ensures
proper bus recovery and avoids potential communication errors
after a conditional reset.

Fixes: 5ea55847 ("i2c: spacemit: add support for SpacemiT K1 SoC")
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>