Bluetooth: Remove rx < tx prio check

The comment states the reason for this requirement is to detect
violations by a remote peer. The ATT version of this was removed in
ea04fd95f9. TLDR: It's neither possible
for, nor the job of the host to police the remote device.

We remove this requirement to be more flexible about the number of
priority levels in the system, and to avoid the temptation of using
priorities as a synchronization mechanism.

Signed-off-by: Aleksander Wasaznik <aleksander.wasaznik@nordicsemi.no>

subsys/bluetooth/common/dummy.c

@@ -23,13 +23,6 @@ BUILD_ASSERT(sizeof(bt_addr_t) == BT_ADDR_SIZE);
 BUILD_ASSERT(sizeof(bt_addr_le_t) == BT_ADDR_LE_SIZE);
 
 #if defined(CONFIG_BT_HCI_HOST)
-/* The Bluetooth subsystem requires the Tx thread to execute at higher priority
- * than the Rx thread as the Tx thread needs to process the acknowledgements
- * before new Rx data is processed. This is a necessity to correctly detect
- * transaction violations in ATT and SMP protocols.
- */
-BUILD_ASSERT(CONFIG_BT_HCI_TX_PRIO < CONFIG_BT_RX_PRIO);
-
 /* The Bluetooth subsystem requires that higher priority events shall be given
  * in a priority higher than the Bluetooth Host's Tx and the Controller's
  * receive thread priority.