common/octeontx2: reduce wait time for mbox messages

After each mbox send operation, context waits for minimum 1ms to get
corresponding response although response can come earlier.
So reducing wait time to lower granularity.

Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>