KVM: Move page fault processing to common code

The code that dispatches the page fault and emulates if we failed to map
is duplicated across vmx and svm.  Merge it to simplify further bugfixing.

Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --cc drivers/kvm/mmu.c
Simple merge

diff --cc drivers/kvm/svm.c
Simple merge

diff --cc drivers/kvm/vmx.c
Simple merge

diff --cc drivers/kvm/x86.h
Simple merge