Aligning configuration to the one introduced in the Zephyr
upmerge.

Signed-off-by: Kamil Kasperczyk <kamil.kasperczyk@nordicsemi.no>

Removed settings default value for the
MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG Kconfig, as it's handled by the
mbedtls module.

With the recent Zephyr upmerge a new boot banner configs were
enabled by default, what results in flash increase and memory
partition overflow. This commit disables newly introduced
configs.

With the recent Zephyr upmerge additional net_if.h includes
are needed for the nrfconnect and Zephyr platforms.