bhyve: fix preprocessor indentation

Syntax-check fails with:

cppi: src/bhyve/bhyve_driver.h: line 26: not properly indented
cppi: src/bhyve/bhyve_driver.h: line 27: not properly indented
maint.mk: incorrect preprocessor indentation

Fix by properly indenting '#include's.

Pushed as trivial.

src/bhyve/bhyve_driver.h

@@ -23,8 +23,8 @@
 #ifndef __BHYVE_DRIVER_H__
 # define __BHYVE_DRIVER_H__
 
-#include "capabilities.h"
-#include "bhyve_utils.h"
+# include "capabilities.h"
+# include "bhyve_utils.h"
 
 int bhyveRegister(void);