bsd-user/main.c: Drop syscall flavor arg -bsd

bsd-user/main.c: Drop syscall flavor arg -bsd

We've not realistically been able to actually run any bsd program on any
other bsd program. They are too diverged to do this easily. The current
code is setup to do it, but implementing it is hard. Stop pretending
that we can do this.

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