Function axdma::phys_to_bus

pub const fn phys_to_bus(paddr: PhysAddr) -> BusAddr

Converts a physical address to a bus address.

It assumes that there is a linear mapping with the offset axconfig::PHYS_BUS_OFFSET, that maps all the physical memory to the virtual space at the address plus the offset. So we have baddr = paddr + PHYS_BUS_OFFSET.