fix(modem): AT-only example: initial adaptation to BG96

Plus rework a little to support implementation of multiple devices

components/esp_modem/examples/modem_tcp_client/main/Kconfig.projbuild

@@ -5,11 +5,6 @@ menu "Example Configuration"
         default EXAMPLE_MODEM_DEVICE_BG96
         help
             Select modem device connected to the ESP DTE.
-        config EXAMPLE_MODEM_DEVICE_SIM800
-            bool "SIM800"
-            help
-                SIMCom SIM800L is a GSM/GPRS module.
-                It supports Quad-band 850/900/1800/1900MHz.
         config EXAMPLE_MODEM_DEVICE_BG96
             bool "BG96"
             help
@@ -26,53 +21,6 @@ menu "Example Configuration"
         help
             Set APN (Access Point Name), a logical name to choose data network
 
-    config EXAMPLE_MODEM_PPP_AUTH_USERNAME
-        string "Set username for authentication"
-        default "espressif"
-        depends on !EXAMPLE_MODEM_PPP_AUTH_NONE
-        help
-            Set username for PPP Authentication.
-
-    config EXAMPLE_MODEM_PPP_AUTH_PASSWORD
-        string "Set password for authentication"
-        default "esp32"
-        depends on !EXAMPLE_MODEM_PPP_AUTH_NONE
-        help
-            Set password for PPP Authentication.
-
-    config EXAMPLE_MODEM_PPP_AUTH_NONE
-        bool "Skip PPP authentication"
-        default n
-        help
-            Set to true for the PPP client to skip authentication
-
-    config EXAMPLE_SEND_MSG
-        bool "Short message (SMS)"
-        default n
-        help
-            Select this, the modem will send a short message before power off.
-
-    if EXAMPLE_SEND_MSG
-        config EXAMPLE_SEND_MSG_PEER_PHONE_NUMBER
-            string "Peer Phone Number (with area code)"
-            default "+8610086"
-            help
-                Enter the peer phone number that you want to send message to.
-    endif
-
-    config EXAMPLE_NEED_SIM_PIN
-        bool "SIM PIN needed"
-        default n
-        help
-            Enable to set SIM PIN before starting the example
-
-    config EXAMPLE_SIM_PIN
-        string "Set SIM PIN"
-        default "1234"
-        depends on EXAMPLE_NEED_SIM_PIN
-        help
-            Pin to unlock the SIM
-
     menu "UART Configuration"
         config EXAMPLE_MODEM_UART_TX_PIN
             int "TXD Pin Number"