KVM: kvm.h: __user requires compiler.h

include/linux/kvm.h defines struct kvm_dirty_log to
	[...]
	union {
		void __user *dirty_bitmap; /* one bit per page */
		__u64 padding;
	};

__user requires compiler.h to compile. Currently, this works on x86
only coincidentally due to other include files. This patch makes
kvm.h compile in all cases.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>