[net][at] Add AT Socket select SAL

Lawlieta · Lawlieta · commit 87c35d4e2f13 · 2018-08-29T20:40:07.000+08:00
diff --git a/components/net/at/Kconfig b/components/net/at/Kconfig
@@ -59,6 +59,7 @@ if RT_USING_AT
         config AT_USING_SOCKET
             bool "Enable BSD Socket API support by AT commnads"
             select RT_USING_LIBC
+            select RT_USING_SAL
             default n
            
     endif
