bsd-user/freebsd/target_os_ucontext.h: Require TARGET_*CONTEXT_SIZE

Now that all architecutres define TARGET_[MU]CONTEXT_SIZE, enforce
requiring them and always check the sizeof target_{u,m}context_t
sizes.

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

bsd-user/freebsd/target_os_ucontext.h

@@ -27,10 +27,8 @@ typedef struct target_ucontext {
     int32_t             __spare__[4];
 } target_ucontext_t;
 
-#ifdef TARGET_MCONTEXT_SIZE
 G_STATIC_ASSERT(TARGET_MCONTEXT_SIZE == sizeof(target_mcontext_t));
 G_STATIC_ASSERT(TARGET_UCONTEXT_SIZE == sizeof(target_ucontext_t));
-#endif /* TARGET_MCONTEXT_SIZE */
 
 struct target_sigframe;