ath11k: Correctly check errors for calls to debugfs_create_dir()

debugfs_create_dir() returns an ERR_PTR in case of error, but never a
null pointer. There are a number of places where error-checking code can
accordingly be simplified.

Addresses-Coverity: CID 1497150: Memory - illegal accesses (USE_AFTER_FREE)
Addresses-Coverity: CID 1497158: Memory - illegal accesses (USE_AFTER_FREE)
Addresses-Coverity: CID 1497160: Memory - illegal accesses (USE_AFTER_FREE)
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200927132451.585473-1-alex.dewar90@gmail.com

drivers/net/wireless/ath/ath11k/debugfs.c

@@ -837,12 +837,8 @@ int ath11k_debugfs_pdev_create(struct ath11k_base *ab)
 		return 0;
 
 	ab->debugfs_soc = debugfs_create_dir(ab->hw_params.name, ab->debugfs_ath11k);
-
-	if (IS_ERR_OR_NULL(ab->debugfs_soc)) {
-		if (IS_ERR(ab->debugfs_soc))
-			return PTR_ERR(ab->debugfs_soc);
-		return -ENOMEM;
-	}
+	if (IS_ERR(ab->debugfs_soc))
+		return PTR_ERR(ab->debugfs_soc);
 
 	debugfs_create_file("simulate_fw_crash", 0600, ab->debugfs_soc, ab,
 			    &fops_simulate_fw_crash);
@@ -863,13 +859,7 @@ int ath11k_debugfs_soc_create(struct ath11k_base *ab)
 {
 	ab->debugfs_ath11k = debugfs_create_dir("ath11k", NULL);
 
-	if (IS_ERR_OR_NULL(ab->debugfs_ath11k)) {
-		if (IS_ERR(ab->debugfs_ath11k))
-			return PTR_ERR(ab->debugfs_ath11k);
-		return -ENOMEM;
-	}
-
-	return 0;
+	return PTR_ERR_OR_ZERO(ab->debugfs_ath11k);
 }
 
 void ath11k_debugfs_soc_destroy(struct ath11k_base *ab)
@@ -1069,13 +1059,8 @@ int ath11k_debugfs_register(struct ath11k *ar)
 	snprintf(pdev_name, sizeof(pdev_name), "%s%d", "mac", ar->pdev_idx);
 
 	ar->debug.debugfs_pdev = debugfs_create_dir(pdev_name, ab->debugfs_soc);
-
-	if (IS_ERR_OR_NULL(ar->debug.debugfs_pdev)) {
-		if (IS_ERR(ar->debug.debugfs_pdev))
-			return PTR_ERR(ar->debug.debugfs_pdev);
-
-		return -ENOMEM;
-	}
+	if (IS_ERR(ar->debug.debugfs_pdev))
+		return PTR_ERR(ar->debug.debugfs_pdev);
 
 	/* Create a symlink under ieee80211/phy* */
 	snprintf(buf, 100, "../../ath11k/%pd2", ar->debug.debugfs_pdev);