The fallback code in cpu_loop_exit_sigsegv is sufficient for
openrisc linux-user.
This makes all of the code in mmu.c sysemu only, so remove
the ifdefs and move the file to openrisc_softmmu_ss.
Remove the code from cpu_loop that handled EXCP_DPF.
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>