[PATCH] MIPS: Set r6 as default arch if vendor is img

[Nick Clifton]

Hi YunQiang Su,

> This behavior is used by downstream toolchain since 2014,
> and has been in GCC since the same year.
> 
> We don't support mips64*-img* due to GCC doesn't support it,
> and we believe that the multilib should be used for this case.

Patch approved and applied.

Cheers
   Nick