[meta-fsl-arm-extra] errors while building boundary kernel 3.14.28

[Carlos Rafael Giani <dv@pseudoterminal.org>]

Hello,

I tried to build an image for a nitrogen6x, using the newest master 
version of Poky, meta-openembedded, and meta-fsl-arm & 
meta-fsl-arm-extra. However, the kernel doesn't compile. I get lots of 
errors like:

| arch/arm/mm/cache-l2x0.o: In function `nop_flush_kern_cache_louis':
| cache-l2x0.c:(.text+0xa38): multiple definition of 
`nop_flush_kern_cache_louis'
| arch/arm/mm/dma-mapping.o:dma-mapping.c:(.text+0x1438): first defined here
| arch/arm/mm/cache-l2x0.o: In function `nop_flush_user_cache_all':
| cache-l2x0.c:(.text+0xa48): multiple definition of 
`nop_flush_user_cache_all'
| arch/arm/mm/dma-mapping.o:dma-mapping.c:(.text+0x1448): first defined here
| arch/arm/mm/cache-l2x0.o: In function `nop_flush_user_cache_range':
| cache-l2x0.c:(.text+0xa58): multiple definition of 
`nop_flush_user_cache_range'
| arch/arm/mm/dma-mapping.o:dma-mapping.c:(.text+0x1458): first defined here

At least one other person apparently had the same problem, since I found 
this log paste: http://pastebin.com/rwu5a6ru

Any ideas what's the cause?