softmmu: introduce cpu_ldst.h

This will collect all load and store helpers soon.  For now
it is just a replacement for softmmu_exec.h, which this patch
stops including directly, but we also include it where this will
be necessary in order to simplify the next patch.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/user-exec.c b/user-exec.c
index 8ed6fec..1ff8673 100644
--- a/user-exec.c
+++ b/user-exec.c
@@ -21,6 +21,7 @@
 #include "disas/disas.h"
 #include "tcg.h"
 #include "qemu/bitops.h"
+#include "exec/cpu_ldst.h"
 
 #undef EAX
 #undef ECX