firmware: cs_dsp: Move lockdep asserts to avoid potential null pointer

Move the lockdep asserts until after the ctl pointer has been checked
for NULL, to avoid potentially NULL pointer dereferences.

Fixes: fb2f364fb5b9 ("firmware: cs_dsp: Add lockdep asserts to interface functions")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20211130102842.26410-1-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: charleskeepax

drivers/firmware/cirrus/cs_dsp.c

@@ -759,11 +759,11 @@ int cs_dsp_coeff_write_ctrl(struct cs_dsp_coeff_ctl *ctl,
 {
 	int ret = 0;
 
-	lockdep_assert_held(&ctl->dsp->pwr_lock);
-
 	if (!ctl)
 		return -ENOENT;
 
+	lockdep_assert_held(&ctl->dsp->pwr_lock);
+
 	if (len + off * sizeof(u32) > ctl->len)
 		return -EINVAL;
 
@@ -827,11 +827,11 @@ int cs_dsp_coeff_read_ctrl(struct cs_dsp_coeff_ctl *ctl,
 {
 	int ret = 0;
 
-	lockdep_assert_held(&ctl->dsp->pwr_lock);
-
 	if (!ctl)
 		return -ENOENT;
 
+	lockdep_assert_held(&ctl->dsp->pwr_lock);
+
 	if (len + off * sizeof(u32) > ctl->len)
 		return -EINVAL;