coresight: stm: Remove redundant NULL checks

container_of() cannot return NULL, so the checks for NULL pointers are
unnecessary and can be safely removed.

As a result, this commit silences the following smatch warnings:

  coresight-stm.c:345 stm_generic_link() warn: can 'drvdata' even be NULL?
  coresight-stm.c:356 stm_generic_unlink() warn: can 'drvdata' even be NULL?
  coresight-stm.c:387 stm_generic_set_options() warn: can 'drvdata' even be NULL?
  coresight-stm.c:422 stm_generic_packet() warn: can 'drvdata' even be NULL?

Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20250611-arm_cs_fix_smatch_warning_v1-v1-1-02a66c69b604@arm.com

Author: Leo-Yan

drivers/hwtracing/coresight/coresight-stm.c

@@ -342,7 +342,7 @@ static int stm_generic_link(struct stm_data *stm_data,
 {
 	struct stm_drvdata *drvdata = container_of(stm_data,
 						   struct stm_drvdata, stm);
-	if (!drvdata || !drvdata->csdev)
+	if (!drvdata->csdev)
 		return -EINVAL;
 
 	return coresight_enable_sysfs(drvdata->csdev);
@@ -353,7 +353,7 @@ static void stm_generic_unlink(struct stm_data *stm_data,
 {
 	struct stm_drvdata *drvdata = container_of(stm_data,
 						   struct stm_drvdata, stm);
-	if (!drvdata || !drvdata->csdev)
+	if (!drvdata->csdev)
 		return;
 
 	coresight_disable_sysfs(drvdata->csdev);
@@ -384,7 +384,7 @@ static long stm_generic_set_options(struct stm_data *stm_data,
 {
 	struct stm_drvdata *drvdata = container_of(stm_data,
 						   struct stm_drvdata, stm);
-	if (!(drvdata && coresight_get_mode(drvdata->csdev)))
+	if (!coresight_get_mode(drvdata->csdev))
 		return -EINVAL;
 
 	if (channel >= drvdata->numsp)
@@ -419,7 +419,7 @@ static ssize_t notrace stm_generic_packet(struct stm_data *stm_data,
 						   struct stm_drvdata, stm);
 	unsigned int stm_flags;
 
-	if (!(drvdata && coresight_get_mode(drvdata->csdev)))
+	if (!coresight_get_mode(drvdata->csdev))
 		return -EACCES;
 
 	if (channel >= drvdata->numsp)