vtop: Multiply by "pagesize" instead of hardcode shift by 12

When convering a page frame number to an address there is a hard-coded
shift by 12 but the mask for the low order bits is computed based on
the "pagesize" variable.

Fix this inconsistency by swapping out the shift for a multiply.

Reported-by: 葛士建 <geshijian@bytedance.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
4 files changed