In the vm domain, where a pair of macros are frequently composed, with inner macro transforming one type to another and then the outer macro transforming that to a third type, define some macros to combine the transformations and allow shorter lines that use them.
Specifically, define VM_PAGE_TO_DMAP and DMAP_TO_VM_PAGE to transform back and forth via the intermediate type PHYS, and use the new macros everywhere they apply. For riscv and arm64 specifically, define PTE_TO_DMAP to compose a pair of transformations via PHYS, and use them where feasible.