qemu-common: stop including qemu/bswap.h from qemu-common.h

Move it to the actual users.  There are still a few includes of
qemu/bswap.h in headers; removing them is left for future work.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/block/vhdx.c b/block/vhdx.c
index ec778fe..c0d24a2 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -22,6 +22,7 @@
 #include "sysemu/block-backend.h"
 #include "qemu/module.h"
 #include "qemu/crc32c.h"
+#include "qemu/bswap.h"
 #include "block/vhdx.h"
 #include "migration/migration.h"