ram_addr_t must be large enough to address any address of the host.

For hosts with sizeof(unsigned long) == sizeof(void *), this patch
changes nothing. All currently supported hosts fall into this category.

For w64 hosts, sizeof(unsigned long) is 4 while sizeof(void *) is 8,
so the use of uintptr_t is needed.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>