kvmclock: use the updated system_timer_msr

kvmclock: use the updated system_timer_msr

Fixes e2b6c17 (kvmclock: update system_time_msr address forcibly)
which makes a call to get the latest value of the address
stored in system_timer_msr, but then uses the old address anyway.

Signed-off-by: Jim Somerville <Jim.Somerville@windriver.com>
Message-Id: <59b67db0bd15a46ab47c3aa657c81a4c11f168ea.1506702472.git.Jim.Somerville@windriver.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 346b1215b1e9f7cc6d8fe9fb6f3c2778b890afb6)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>