[build] Avoid modifying load addresses when stripping .zinfo section

[build] Avoid modifying load addresses when stripping .zinfo section

Some versions of objcopy will spuriously complain when asked to
extract the .zinfo section since doing so will nominally alter the
load addresses of the (non-loadable) .bss.* sections.

Avoid these warnings by placing the .zinfo section at the very end of
the load memory address space.

Allocate non-overlapping load memory addresses for the (non-loadable)
.bss.* sections, in the hope of avoiding spurious warnings about
overlapping load addresses.

Signed-off-by: Michael Brown <mcb30@ipxe.org>