make X25519 & Ed25519 available for mbedtls configurations

[sa-kib]

Make LTC implementations of X25519 & Ed25519 algorithms available when crypto library is chosen to be mbedtls (which yet lacks support for these algorithms).

[jforissier]

Make LTC implementations of X25519 & Ed25519 algorithms available when crypto library is chosen to be mbedtls (which yet lacks support for these algorithms).

That's fine (Acked-by: Jerome Forissier <jerome.forissier@linaro.org>), but wouldn't it make more sense to have this commit after some other commit actually adding/enabling support in MBed TLS ?

[sa-kib]

Make LTC implementations of X25519 & Ed25519 algorithms available when crypto library is chosen to be mbedtls (which yet lacks support for these algorithms).

That's fine (Acked-by: Jerome Forissier <jerome.forissier@linaro.org>), but wouldn't it make more sense to have this commit after some other commit actually adding/enabling support in MBed TLS ?

@jforissier this PR is actually a follow up of this discussion. Probably the commit description is a bit misleading, so I changed it for more clarity.

[jforissier]

@sa-kib thanks for the update but I still find the commit description unclear. I'd like to make sure I understand well: this patch allows LibTomCrypt to be used for X25519/Ed25519 when MBedTLS is selected, correct? In this case how about:

crypto: fallback to LibTomCrypt for X25519/Ed25519 when CFG_CRYPTOLIB_NAME=mbedtls

Mbed TLS currently does not support X25519/Ed25519. This commit allows the
use of LibTomCrypt for these algorithms when CFG_CRYPTO_ED25519=y and/or
CFG_CRYPTO_X25519=y, and CFG_CRYPTOLIB_NAME=mbedtls.

[sa-kib]

@sa-kib thanks for the update but I still find the commit description unclear. I'd like to make sure I understand well: this patch allows LibTomCrypt to be used for X25519/Ed25519 when MBedTLS is selected, correct? In this case how about:

crypto: fallback to LibTomCrypt for X25519/Ed25519 when CFG_CRYPTOLIB_NAME=mbedtls

Mbed TLS currently does not support X25519/Ed25519. This commit allows the
use of LibTomCrypt for these algorithms when CFG_CRYPTO_ED25519=y and/or
CFG_CRYPTO_X25519=y, and CFG_CRYPTOLIB_NAME=mbedtls.

I think your version describes what's going on very nice, I shall use it (only added word 'implementation' to clarify that only a part of LibTomCrypt gets enabled)