pbio/include/pbdrv/cache.h: Mark .dma section as ELF NOBITS

Otherwise the section attributes will default to PROGBITS and
cause the entire .bss section to be filled with 0s *on disk*,
thus bloating the firmware.elf file.

Author: ArcaneNibble

lib/pbio/include/pbdrv/cache.h

@@ -34,6 +34,6 @@ void pbdrv_cache_prepare_after_dma(const void *buf, size_t sz);
 #define PBDRV_CACHE_LINE_SZ         32
 
 // Align data to a cache line, which is needed for clean RX DMA
-#define PBDRV_DMA_BUF               __attribute__((aligned(PBDRV_CACHE_LINE_SZ), section(".dma")))
+#define PBDRV_DMA_BUF               __attribute__((aligned(PBDRV_CACHE_LINE_SZ), section(".dma,\"aw\",%nobits@")))
 
 #endif