[U-Boot] GCC 5.x compile errors

Attempted to build u-boot with gcc 5.x for mipsel 32. Result was that I get brokenness around arch/mips/include/asm/io.h and arch/mips/include/asm/system.h. The source lines all look something like:

extern inline void func() { func text ; }

Question: Is that valid C text? I have never seen such. Also, what does this mean from a header file? The way I read this is

extern = the following declare exists in global space (no code here)

inline = use this function definition in line in place of creating a text ref section

I would expect these two to be mutually exclusive????

Please enlighten me!

Thanks, Andy