[ALSA] Remove sound/driver.h

This header file exists only for some hacks to adapt alsa-driver
tree.  It's useless for building in the kernel.  Let's move a few
lines in it to sound/core.h and remove it.
With this patch, sound/driver.h isn't removed but has just a single
compile warning to include it.  This should be really killed in
future.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

sound/drivers/mpu401/mpu401.c

@@ -20,7 +20,6 @@
  *
  */
 
-#include <sound/driver.h>
 #include <linux/init.h>
 #include <linux/pnp.h>
 #include <linux/err.h>

sound/drivers/mpu401/mpu401_uart.c

@@ -28,7 +28,6 @@
  *
  */
 
-#include <sound/driver.h>
 #include <asm/io.h>
 #include <linux/delay.h>
 #include <linux/init.h>