modules: mbedtls: fix MBEDTLS_PSA_P256M_DRIVER_RAW Kconfig option

Make it depend on MBEDTLS_PSA_P256M_DRIVER_ENABLED instead of
selecting it.

This fixes the build of
tests/crypto/secp256r1/crypto.secp256r1.p256-m_raw on filtered-out
platforms since PR #75441 (83cd9f5a).

Signed-off-by: Tomi Fontanilles <tomi.fontanilles@nordicsemi.no>