coresight: Fix dsb_mode_store() unsigned val is never less than zero

dsb_mode_store() warn: unsigned 'val' is never less than zero.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410150702.UaZ7kvet-lkp@intel.com/
Fixes: 018e43a ("coresight-tpdm: Add node to set dsb programming mode")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/122503017ada249fbf12be3fa4ee6ccb8f8c78cc.1732156624.git.xiaopei01@kylinos.cn

Author: Pei Xiao

drivers/hwtracing/coresight/coresight-tpdm.c

@@ -640,8 +640,7 @@ static ssize_t dsb_mode_store(struct device *dev,
 	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	unsigned long val;
 
-	if ((kstrtoul(buf, 0, &val)) || (val < 0) ||
-			(val & ~TPDM_DSB_MODE_MASK))
+	if ((kstrtoul(buf, 0, &val)) || (val & ~TPDM_DSB_MODE_MASK))
 		return -EINVAL;
 
 	spin_lock(&drvdata->spinlock);