KVM: VMX: Remove ple_window_actual_max

Get rid of ple_window_actual_max, because its benefits are really
minuscule and the logic is complicated.

The overflows(and underflow) are controlled in __ple_window_grow
and _ple_window_shrink respectively.

Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
[Fixed potential wraparound and change the max to UINT_MAX. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>