[nrf fromtree] sampes/smp_svr: Bring back UART shell when using BT transport

Adding configuration options to bring old behaviour where
UART shell have been available when overlay-bt.conf has been
used for building sample.

[nrf] Adapted to use non-revamped MCUmgr symbols.

Signed-off-by: Dominik Ermel <[email protected]>
Signed-off-by: Jamie McCrae <[email protected]>
(cherry picked from commit 26d32bd)

Author: nordicjm

samples/subsys/mgmt/mcumgr/smp_svr/overlay-bt.conf

@@ -13,6 +13,8 @@ CONFIG_MCUMGR_SMP_BT_AUTHEN=n
 CONFIG_MCUMGR_SMP_BT_CONN_PARAM_CONTROL=y
 
 # Enable the Shell mcumgr transport.
+CONFIG_SHELL=y
+CONFIG_SHELL_BACKEND_SERIAL=y
 CONFIG_MCUMGR_SMP_SHELL=y
 
 # Enable the mcumgr Packet Reassembly feature over Bluetooth and its configuration dependencies.