arch: arm: core: fix vector table relocate write to flash

Some SOCs (e.g. STM32F0) can map the flash to address 0 and
the flash base address at the same time. Prevent writing to
duplicate flash address which stops the SOC.

Allow Cortex M SOCs to create their own vector table relocation
function.

Provide a relocation function for STM32F0x SOCs.

Fixes #3923

Signed-off-by: Bobby Noelte <b0661n0e17e@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>