hw/arm/sysbus-fdt: Replace error_setg(&error_fatal) by error_report() + exit()

hw/arm/sysbus-fdt: Replace error_setg(&error_fatal) by error_report() + exit()

Use error_report() + exit() instead of error_setg(&error_fatal),
as suggested by the "qapi/error.h" documentation:

   Please don't error_setg(&error_fatal, ...), use error_report() and
   exit(), because that's more obvious.

This fixes CID 1352173:
    "Passing null pointer dt_name to qemu_fdt_node_path, which dereferences it."

And this also fixes:

    hw/arm/sysbus-fdt.c:322:9: warning: Array access (from variable 'node_path') results in a null pointer dereference
        if (node_path[1]) {
            ^~~~~~~~~~~~

Fixes: Coverity CID 1352173 (Dereference after null check)
Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20180625165749.3910-3-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>