vm_phys: Fix vm_phys_find_range() after commit 69cbb18746b6

vm_phys_seg_paddr_to_vm_page() expects a PA that's in bounds, but
vm_phys_find_range() purposefully returns a pointer to the end of the
last page in a segment.

Fixes: 69cbb18746b6 ("vm_phys: Add a vm_phys_seg_paddr_to_vm_page() helper")