bsd-user; Update the definitions of __put_user and __get_user macros

Use __builtin_choose_expr to avoid type promotion from ?:
in __put_user_e and __get_user_e macros.
Copied from linux-user/qemu.h, originally by Blue Swirl.

Signed-off-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>