Bluetooth: SMP: Fix assumption of Central always being Initiator

[ Upstream commit 28cd47f75185c4818b0fb1b46f2f02faaba96376 ]

SMP initiator role shall be considered the one that initiates the
pairing procedure with SMP_CMD_PAIRING_REQ:

BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 3, Part H
page 1557:

Figure 2.1: LE pairing phases

Note that by sending SMP_CMD_SECURITY_REQ it doesn't change the role to
be Initiator.

Link: https://github.com/bluez/bluez/issues/567
Fixes: b28b4943

 ("Bluetooth: Add strict checks for allowed SMP PDUs")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>