KVM: struct kvm_memory_slot.flags -> u32

struct kvm_userspace_memory_region.flags is a u32 with a comment that
bits 0 ~ 15 are visible to userspace and the other bits are reserved
for kvm internal use.  KVM_MEMSLOT_INVALID is the only internal use
flag and it has a comment that bits 16 ~ 31 are internally used and
the other bits are visible to userspace.

Therefore, let's define this as a u32 so we don't waste bytes on LP64
systems.  Move to the end of the struct for alignment.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

include/linux/kvm_host.h

@@ -266,10 +266,10 @@ static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu)
 struct kvm_memory_slot {
 	gfn_t base_gfn;
 	unsigned long npages;
-	unsigned long flags;
 	unsigned long *dirty_bitmap;
 	struct kvm_arch_memory_slot arch;
 	unsigned long userspace_addr;
+	u32 flags;
 	int id;
 	bool user_alloc;
 };