sound: oss: mpu401.c: Cleaning up missing break in a case

Added a missed break in a case statement

This was found using a static code analysis program called cppcheck.

Signed-off-by: Rickard Strandqvist <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/oss/mpu401.c

···
 				case 0xf6:
 					/* printk( "tune_request\n"); */
 					devc->m_state = ST_INIT;
+					break;
 
 					/*
 					 *    Real time messages