zephyr: select USE_DT_CODE_PARTITION after kconfig option change

Zephyr commit [1] has changed kconfig option name. Update kconfig
selection to the new one.

[1] 90b9eb3a9e93 ("kconfig: Rename USE_CODE_PARTITION to
  USE_DT_CODE_PARTITION")

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>