ahci: Use virt_to_phys() to denote physical addresses for DMA

ahci: Use virt_to_phys() to denote physical addresses for DMA

Update the assignment of various physical memory buffers used by the
SATA controller to explicitly be denoted as physical addresses.

The memory is identity-mapped, so these function calls are a nop, but
they provide good semantic documentation for any maintainers.

The return value of virt_to_phys() is 'unsigned long'.  On machines
where sizeof(unsigned long) != sizeof(pointer), a cast through
(uintptr_t) is needed to appease the compiler due to the potential of
losing the upper 32 bits of the address.

In compilation this scenario, a physical address could be 64-bits, yet
the C pointer environment only allows 32-bit addresses; the constraint
is that pointers cannot address more than 4Gb of memory and if
virt_to_phys() ever returns an out-of-range value for the physical
address, there are issues with emmory mapping which must be solved.
However, since the memory is identify mappeed, there is no problem
introducing the cast: the original pointer will reside in 32-bits, so
the physical address will also be within in 32-bits.

Signed-off-by: Taylor Hutt <thutt@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>