Various drivers' irq handlers: kill dead code, needless casts

- Eliminate casts to/from void*

- Eliminate checks for conditions that never occur.  These typically
  fall into two classes:

	1) Checking for 'dev_id == NULL', then it is never called with
	NULL as an argument.

	2) Checking for invalid irq number, when the only caller (the
	system) guarantees the irq handler is called with the proper
	'irq' number argument.

Signed-off-by: Jeff Garzik <jeff@garzik.org>

sound/oss/es1371.c

@@ -1102,7 +1102,7 @@ static void es1371_handle_midi(struct es1371_state *s)
 
 static irqreturn_t es1371_interrupt(int irq, void *dev_id)
 {
-        struct es1371_state *s = (struct es1371_state *)dev_id;
+        struct es1371_state *s = dev_id;
 	unsigned int intsrc, sctl;
 	
 	/* fastpath out, to ease interrupt sharing */

sound/oss/hal2.c

@@ -372,7 +372,7 @@ static void hal2_adc_interrupt(struct hal2_codec *adc)
 
 static irqreturn_t hal2_interrupt(int irq, void *dev_id)
 {
-	struct hal2_card *hal2 = (struct hal2_card*)dev_id;
+	struct hal2_card *hal2 = dev_id;
 	irqreturn_t ret = IRQ_NONE;
 
 	/* decide what caused this interrupt */

sound/oss/i810_audio.c

@@ -1525,7 +1525,7 @@ static void i810_channel_interrupt(struct i810_card *card)
 
 static irqreturn_t i810_interrupt(int irq, void *dev_id)
 {
-	struct i810_card *card = (struct i810_card *)dev_id;
+	struct i810_card *card = dev_id;
 	u32 status;
 
 	spin_lock(&card->lock);

sound/oss/mpu401.c

@@ -435,7 +435,7 @@ static void mpu401_input_loop(struct mpu_config *devc)
 static irqreturn_t mpuintr(int irq, void *dev_id)
 {
 	struct mpu_config *devc;
-	int dev = (int) dev_id;
+	int dev = (int)(unsigned long) dev_id;
 	int handled = 0;
 
 	devc = &dev_conf[dev];

sound/oss/vwsnd.c

@@ -2235,7 +2235,7 @@ static void vwsnd_audio_write_intr(vwsnd_dev_t *devc, unsigned int status)
 
 static irqreturn_t vwsnd_audio_intr(int irq, void *dev_id)
 {
-	vwsnd_dev_t *devc = (vwsnd_dev_t *) dev_id;
+	vwsnd_dev_t *devc = dev_id;
 	unsigned int status;
 
 	DBGEV("(irq=%d, dev_id=0x%p)\n", irq, dev_id);