target/alpha: Implement alpha_cpu_record_sigbus

Record trap_arg{0,1,2} for the linux-user signal frame.

Raise SIGBUS directly from cpu_loop_exit_sigbus, which means
we can remove the code for EXCP_UNALIGN in cpu_loop.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
4 files changed