Remove sparc_opcode_archs and the macros which use it, because we don't
use them in QEMU and they provoke clang warnings:

disas/sparc.c:307:39: warning: unused variable 'sparc_opcode_archs' [-Wunused-const-variable]
static const struct sparc_opcode_arch sparc_opcode_archs[] =
                                      ^

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>