Xtensa configuration overlays for recent releases may have special
registers for which [rwx]sr opcodes are defined, but they are not listed
as SR in xtensa_sysreg_name and associated functions. As a result
generic translate_[rwx]sr* functions generate access to uninitialized
cpu_SR causing segfault at runtime.
Don't try to access cpu_SR for such registers, ignore writes and return
0 for reads.
Cc: qemu-stable@nongnu.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
59afd43dae