microblaze: boot: Don't hack the elf entry point

There was some modulo logic to ensure that Microblaze always booted into
physical RAM regardless of the elf entry. Removed it, as QEMU should fail
gracefully when given a bad elf, rather than attempt to run it.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
