boot/zephyr: set VTOR to relay vector before chain-load
boot/zephyr: set VTOR to relay vector before chain-load

If software IRQ relay is enabled and VTOR is available,
the bootloader will switch from its real vector table
to the relay vector table before chain-loading to the
application.

Signed-off-by: Rafał Kuźnia <2e7ab041a15fd1b2ee150a94889a37d823e289e8@nordicsemi.no>
Signed-off-by: Krzysztof Taborowski <d1665fc2a4f9428720cda5e5534f33d21cf6b684@nordicsemi.no>
Signed-off-by: Andrzej Puzdrowski <0222c24e1773dd88269ed0e559909ec9bea3604a@nordicsemi.no>

utzig/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,utzig/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,runtimeco/mcuboot,tamban01/mcuboot,ATmobica/mcuboot,runtimeco/mcuboot,utzig/mcuboot,runtimeco/mcuboot,ATmobica/mcuboot,tamban01/mcuboot,utzig/mcuboot,ATmobica/mcuboot,utzig/mcuboot,runtimeco/mcuboot