x86: Increase the size of the phys_size_t and phys_addr_t types

These types should be 64 bits long to reflect the fact that physical
addresses and the size of physical areas of memory are more than 32 bits
long.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>