stm32/boards/PYBD_SF2: Put nimble library in external QSPI XIP flash.

The BLE stack is not performance critical, so put it in external
memory-mapped flash to save internal flash for other things (like frozen
bytecode).

ports/stm32/boards/PYBD_SF2/f722_qspi.ld

@@ -49,6 +49,7 @@ SECTIONS
     {
         . = ALIGN(4);
         *lib/mbedtls/*(.text* .rodata*)
+        *lib/mynewt-nimble/*(.text* .rodata*)
         . = ALIGN(512);
         *(.big_const*)
         . = ALIGN(4);