Include hw/hw.h exactly where needed

In my "build everything" tree, changing hw/hw.h triggers a recompile
of some 2600 out of 6600 objects (not counting tests and objects that
don't depend on qemu/osdep.h).

The previous commits have left only the declaration of hw_error() in
hw/hw.h.  This permits dropping most of its inclusions.  Touching it
now recompiles less than 200 objects.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20190812052359.30071-19-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>

include/hw/audio/pcspk.h

@@ -25,7 +25,6 @@
 #ifndef HW_PCSPK_H
 #define HW_PCSPK_H
 
-#include "hw/hw.h"
 #include "hw/isa/isa.h"
 
 #define TYPE_PC_SPEAKER "isa-pcspk"

include/hw/audio/wm8750.h

@@ -14,7 +14,6 @@
 #ifndef HW_DAC_WM8750_H
 #define HW_DAC_WM8750_H
 
-#include "hw/hw.h"
 
 #define TYPE_WM8750 "wm8750"
 #define TYPE_MV88W8618_AUDIO "mv88w8618_audio"