Enable mailbox configs for Versal NET.

Signed-off-by: Jay Buddhabhatti <jay.buddhabhatti@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/b3a9a6a58b74d17e2ec5f60617fa42062fbab951.1663589964.git.michal.simek@amd.com