linux-user: Remove HAVE_SAFE_SYSCALL and hostdep.h

All supported hosts now define HAVE_SAFE_SYSCALL, so remove
the ifdefs.  This leaves hostdep.h empty, so remove it.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/linux-user/safe-syscall.h b/linux-user/safe-syscall.h
index 97837fa..f43267a 100644
--- a/linux-user/safe-syscall.h
+++ b/linux-user/safe-syscall.h
@@ -124,7 +124,7 @@
  * need to check SA_RESTART flags in QEMU or distinguish the various
  * kinds of restartability.
  */
-#ifdef HAVE_SAFE_SYSCALL
+
 /* The core part of this function is implemented in assembly */
 extern long safe_syscall_base(int *pending, long number, ...);
 extern long safe_syscall_set_errno_tail(int value);
@@ -137,15 +137,4 @@
     safe_syscall_base(&((TaskState *)thread_cpu->opaque)->signal_pending, \
                       __VA_ARGS__)
 
-#else
-
-/*
- * Fallback for architectures which don't yet provide a safe-syscall assembly
- * fragment; note that this is racy!
- * This should go away when all host architectures have been updated.
- */
-#define safe_syscall syscall
-
-#endif
-
 #endif