hw/core/loader: implement address translation in uimage loader

Such address translation is needed when load address recorded in uImage
is a virtual address. When the actual load address is requested, return
untranslated address: user that needs the translated address can always
apply translation function to it and those that need it untranslated
don't need to do the inverse translation.

Add translation function pointer and its parameter to uimage_load
prototype. Update all existing users.

No user-visible functional changes.

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
hw/xtensa/xtfpga: treat uImage load address as virtual

U-boot for xtensa always treats uImage load address as virtual address.
This is important when booting uImage on xtensa core with MMUv2, because
MMUv2 has fixed non-identity virtual-to-physical mapping after reset.

Always do virtual-to-physical translation of uImage load address and
load uImage at the translated address. This fixes booting uImage kernels
on dc232b and other MMUv2 cores.

Cc: qemu-stable@nongnu.org
Reported-by: Waldemar Brodkorb <mail@waldemar-brodkorb.de>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>