scsi: megaraid_mbox: Avoid double kfree()

Smatch found a double-free after my recent change:

	drivers/scsi/megaraid/megaraid_mbox.c:3474 megaraid_cmm_register()
	error: double free of 'adp' (line 3468)

Since the object is no longer allocated in megaraid_cmm_register(),
remove the kfree() as well.

Fixes: c1f7275 ("scsi: megaraid_mbox: Reduce stack usage in megaraid_cmm_register()")
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260601210216.846809-1-arnd@kernel.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: arndb

drivers/scsi/megaraid/megaraid_mm.c

@@ -998,8 +998,6 @@ mraid_mm_register_adp(mraid_mmadp_t *adapter)
 
 	dma_pool_destroy(adapter->pthru_dma_pool);
 
-	kfree(adapter);
-
 	return rval;
 }