s390/qeth: Make hw_trap sysfs attribute idempotent

Update qeth driver to allow writing an existing value to the "hw_trap"
sysfs attribute. Attempting such a write earlier resulted in -EINVAL.
In other words, make the sysfs attribute idempotent.

After:
    $ cat hw_trap
    disarm
    $ echo disarm > hw_trap
    $

Suggested-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Aswin Karuvally <aswin@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250718141711.1141049-1-wintera@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Aswin Karuvally

drivers/s390/net/qeth_core_sys.c

@@ -518,28 +518,32 @@ static ssize_t qeth_hw_trap_store(struct device *dev,
 	if (qeth_card_hw_is_reachable(card))
 		state = 1;
 
-	if (sysfs_streq(buf, "arm") && !card->info.hwtrap) {
-		if (state) {
+	if (sysfs_streq(buf, "arm")) {
+		if (state && !card->info.hwtrap) {
 			if (qeth_is_diagass_supported(card,
 			    QETH_DIAGS_CMD_TRAP)) {
 				rc = qeth_hw_trap(card, QETH_DIAGS_TRAP_ARM);
 				if (!rc)
 					card->info.hwtrap = 1;
-			} else
+			} else {
 				rc = -EINVAL;
-		} else
+			}
+		} else {
 			card->info.hwtrap = 1;
-	} else if (sysfs_streq(buf, "disarm") && card->info.hwtrap) {
-		if (state) {
+		}
+	} else if (sysfs_streq(buf, "disarm")) {
+		if (state && card->info.hwtrap) {
 			rc = qeth_hw_trap(card, QETH_DIAGS_TRAP_DISARM);
 			if (!rc)
 				card->info.hwtrap = 0;
-		} else
+		} else {
 			card->info.hwtrap = 0;
-	} else if (sysfs_streq(buf, "trap") && state && card->info.hwtrap)
+		}
+	} else if (sysfs_streq(buf, "trap") && state && card->info.hwtrap) {
 		rc = qeth_hw_trap(card, QETH_DIAGS_TRAP_CAPTURE);
-	else
+	} else {
 		rc = -EINVAL;
+	}
 
 	mutex_unlock(&card->conf_mutex);
 	return rc ? rc : count;