microblaze: Do not copy reset vectors/manual reset vector setup

Reset vector can be setup by bootloader and kernel doens't need
to touch it. If you require to setup reset vector, please use
CONFIG_MANUAL_RESET_VECTOR throught menuconfig.
It is not possible to setup address 0x0 as reset address because
make no sense to set it up at all.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: John Williams <john.williams@petalogix.com>