accel/amdxdna: Clear mailbox interrupt register during channel creation

The mailbox interrupt register is not always cleared when a mailbox channel
is created. This can leave stale interrupt states from previous operations.

Fix this by explicitly clearing the interrupt register in the mailbox
channel creation function.

Fixes: b87f920b9344 ("accel/amdxdna: Support hardware mailbox")
Reviewed-by: Maciej Falkowski <[e-mail]>
Signed-off-by: Lizhi Hou <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/accel/amdxdna/amdxdna_mailbox.c

···
 	}
 
 	mb_chann->bad_state = false;
+	mailbox_reg_write(mb_chann, mb_chann->iohub_int_addr, 0);
 
 	MB_DBG(mb_chann, "Mailbox channel created (irq: %d)", mb_chann->msix_irq);
 	return mb_chann;