Fix una_asm.S

The version of this file in newer kernels lacks these underscores, so I
assume something changed at some point.  Without this change this kernel
doesn't compile.
Remove -Werror from some arch/sparc64 Makefiles

These proved a mite too optimistic for the version of the compiler I'm
using.  This is the type of cleanup you end up doing for kernels
released over half a decade ago, I guess.