boards: infineon: cyw920829m2: Fix unit and first address mismatch

This fixes the following warning:

> unit address and first address in 'reg' (0x60000) don't match for
> /qspi_flash@40890000/flash@60000000/partitions/storage_partition@70000

Signed-off-by: Reto Schneider <reto.schneider@husqvarnagroup.com>