arch/x86: Fix MSI MAP destination

When Zephyr runs directly on actual hardware, it will be always
directing MSI messages to BSP (BootStrap Processor). This was fine until
Zephyr could be ran on virtualizor that may NOT run it on BSP.

So directing MSI messages on current processor. If Zephyr runs on actual
hardware, it will be BSP since such setup is always made at boot time by
the BSP. On other use case it will be whatever is relevant at that time.

Fixes #43853

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>