char/mwave: turn tp3780I_Cleanup() into void function

This function always return '0' and no callers use the return value.
So make it a void function.

This eliminates the following coccicheck warning:
./drivers/char/mwave/tp3780i.c:182:5-11: Unneeded variable: "retval".
Return "0" on line 187

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Yang Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/char/mwave/tp3780i.c

···
 	return retval;
 }
 
-int tp3780I_Cleanup(THINKPAD_BD_DATA * pBDData)
+void tp3780I_Cleanup(THINKPAD_BD_DATA *pBDData)
 {
-	int retval = 0;
-
 	PRINTK_2(TRACE_TP3780I,
 		"tp3780i::tp3780I_Cleanup entry and exit pBDData %p\n", pBDData);
-
-	return retval;
 }
 
 int tp3780I_CalcResources(THINKPAD_BD_DATA * pBDData)

drivers/char/mwave/tp3780i.h

···
 int tp3780I_ResetDSP(THINKPAD_BD_DATA * pBDData);
 int tp3780I_StartDSP(THINKPAD_BD_DATA * pBDData);
 int tp3780I_QueryAbilities(THINKPAD_BD_DATA * pBDData, MW_ABILITIES * pAbilities);
-int tp3780I_Cleanup(THINKPAD_BD_DATA * pBDData);
+void tp3780I_Cleanup(THINKPAD_BD_DATA *pBDData);
 int tp3780I_ReadWriteDspDStore(THINKPAD_BD_DATA * pBDData, unsigned int uOpcode,
                                void __user *pvBuffer, unsigned int uCount,
                                unsigned long ulDSPAddr);