This patch extends trace_kvm_exit() to include KVM exit reasons
(i.e. EC of HSR). The tracing function then dumps both exit reason
and PC of vCPU, shown as the following. Tracing tools can use this
new exit_reason field to better understand the behavior of guest VMs.

886.301252: kvm_exit:             HSR_EC: 0x0024, PC: 0xfffffe0000506b28
Signed-off-by: NWei Huang <wei@redhat.com>
Signed-off-by: NChristoffer Dall <christoffer.dall@linaro.org>