Rearrange block headers

Changing block.h or blockdev.h resulted in recompiling most objects.

Move DriveInfo typedef and BlockInterfaceType enum definitions
to qemu-common.h and rearrange blockdev.h use to decrease churn.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/mips_r4k.c b/hw/mips_r4k.c
index 61cd33a..ca61431 100644
--- a/hw/mips_r4k.c
+++ b/hw/mips_r4k.c
@@ -22,6 +22,7 @@
 #include "loader.h"
 #include "elf.h"
 #include "mc146818rtc.h"
+#include "blockdev.h"
 
 #define MAX_IDE_BUS 2