hv: modularization: cleanup boot.h

Move multiboot specific declarations from boot.h to multiboot.h.

Tracked-On: #5661
Signed-off-by: Vijay Dhanraj <vijay.dhanraj@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>

hypervisor/boot/multiboot/multiboot2.c

@@ -7,6 +7,7 @@
 #include <types.h>
 #include <errno.h>
 #include <boot.h>
+#include <multiboot.h>
 #include <pgtable.h>
 #include "multiboot_priv.h"