mbedtls: compile FFDH support in PSA mode

Include `psa_crypto_ffdh.c` when compiling MbedTLS with PSA support, as
`MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY` references the included
functions.

Signed-off-by: Jordan Yates <jordan@embeint.com>
1 file changed