vvmx: fixes after CR4 trapping optimizations

vvmx: fixes after CR4 trapping optimizations

Commit 40681735502 doesn't update nested VMX code in order to
take into account L1 CR4 host mask when nested guest (L2) writes
to CR4, and thus the mask written to CR4_GUEST_HOST_MASK is
likely not as restrictive as it should be.

Also the VVMCS GUEST_CR4 value should be updated to match the
underlying value when syncing the VVMCS state.

Fixes: 40681735502 ("vmx/hap: optimize CR4 trapping")
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>