sound: oss: mpu401.c: Cleaning up variable is set more than once

A struct member variable is set to the same value more than once

This was found using a static code analysis program called cppcheck.
Signed-off-by: NRickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/oss/mpu401.c

@@ -973,7 +973,6 @@ int attach_mpu401(struct address_info *hw_config, struct module *owner)
 	devc->m_busy = 0;
 	devc->m_state = ST_INIT;
 	devc->shared_irq = hw_config->always_detect;
-	devc->irq = hw_config->irq;
 	spin_lock_init(&devc->lock);
 
 	if (devc->irq < 0)