In psa_generate_key_internal() for ECC keys, remove the check that the
bit-size according to Mbed TLS is equal to the requested bit-size.
This check was necessary back when the PSA API encoded curves and key
sizes independently, in order to reject combinations such as SECP256R1
with a 512-bit size. Since the curve encoding changed to specifying a
curve family and a size separately, the Mbed TLS curve id (grp_id) and
the curve data (curve_info) are now determined from the size, and
checking that (curve_info->bit_size == bits) is now only a redundant
sanity check.
This check is actually buggy, because PSA Crypto and Mbed TLS don't
have exactly the same notion of key size. PSA thinks Curve25519 is
255-bit and secp224k1 is 225-bit, but Mbed TLS thinks they're 256-bit
and 224-bit respectively. Removing the check allows key generation to
work for these curves.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
