rp2/main: Keep UART REPL with DEBUG=1 and MICROPY_HW_ENABLE_UART_REPL=1.

For builds with DEBUG=1 and MICROPY_HW_ENABLE_UART_REPL=1, calling
stdio_init_all() in main() detaches the UART input from REPL.  This change
suppresses calling stdio_init_all() then.

ports/rp2/main.c

@@ -76,6 +76,10 @@ int main(int argc, char **argv) {
     bi_decl(bi_program_feature("UART REPL"))
     setup_default_uart();
     mp_uart_init();
+    #else
+    #ifndef NDEBUG
+    stdio_init_all();
+    #endif
     #endif
 
     #if MICROPY_HW_ENABLE_USBDEV
@@ -90,10 +94,6 @@ int main(int argc, char **argv) {
     mp_thread_init();
     #endif
 
-    #ifndef NDEBUG
-    stdio_init_all();
-    #endif
-
     // Start and initialise the RTC
     datetime_t t = {
         .year = 2021,