bsd-user/x86_64/target_arch_signal.h: Remove target_sigcontext

In FreeBSD, sigcontext was retired in favor of ucontext/mcontext.
Remove vestigial target_sigcontext.

Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed