pbio/platform/ev3/platform.ld: Ensure .bss is NOLOAD

Otherwise the recent addition of the .dma section defaults to PROGBITS
and causes the entire .bss section to be filled with 0s *on disk*,
thus bloating the firmware.elf file.

Author: ArcaneNibble

lib/pbio/platform/ev3/platform.ld

@@ -60,7 +60,7 @@ SECTIONS
         *(.data.*)
     } > DDR
 
-    .bss :
+    .bss (NOLOAD) :
     {
         . = ALIGN(4);
         _bss_start = .;