uio: uio_dmem_genirq: Use non-atomic bit operations in irq config and handling

This finishes the port of the irq configuration and handling from
"uio_pdrv_genirq" to "uio_dmem_genirq". It changes the atomic
bit-manipulation routines to their non-atomic counterparts as we are
already guarding the code by spinlock.

Split out from commit 34cb27528398 ("UIO: Fix concurrency issue").

Signed-off-by: Rafael Mendonca <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/uio/uio_dmem_genirq.c

···
 	unsigned int refcnt;
 };
 
+/* Bits in uio_dmem_genirq_platdata.flags */
+enum {
+	UIO_IRQ_DISABLED = 0,
+};
+
 static int uio_dmem_genirq_open(struct uio_info *info, struct inode *inode)
 {
 	struct uio_dmem_genirq_platdata *priv = info->priv;
···
 	 */
 
 	spin_lock(&priv->lock);
-	if (!test_and_set_bit(0, &priv->flags))
+	if (!__test_and_set_bit(UIO_IRQ_DISABLED, &priv->flags))
 		disable_irq_nosync(irq);
 	spin_unlock(&priv->lock);
 
···
 
 	spin_lock_irqsave(&priv->lock, flags);
 	if (irq_on) {
-		if (test_and_clear_bit(0, &priv->flags))
+		if (__test_and_clear_bit(UIO_IRQ_DISABLED, &priv->flags))
 			enable_irq(dev_info->irq);
 	} else {
-		if (!test_and_set_bit(0, &priv->flags))
+		if (!__test_and_set_bit(UIO_IRQ_DISABLED, &priv->flags))
 			disable_irq_nosync(dev_info->irq);
 	}
 	spin_unlock_irqrestore(&priv->lock, flags);