mailbox: arm_mhu: reduce txpoll_period from 10ms to 1 ms

Since the mailbox core users hrtimers now, it can handle much higher
resolutions. We can reduce the txpoll_period to 1 ms as the transmit
usually takes just few microseconds.

Reported-and-suggested-by: Juri Lelli <[e-mail]>
Signed-off-by: Sudeep Holla <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

drivers/mailbox/arm_mhu.c

···
 	mhu->mbox.ops = &mhu_ops;
 	mhu->mbox.txdone_irq = false;
 	mhu->mbox.txdone_poll = true;
-	mhu->mbox.txpoll_period = 10;
+	mhu->mbox.txpoll_period = 1;
 
 	amba_set_drvdata(adev, mhu);