MBEDTLS_PK_PARSE_EC_EXTENDED is incompatible with MBEDTLS_ECP_ALT
MBEDTLS_PK_PARSE_EC_EXTENDED is incompatible with MBEDTLS_ECP_ALT

... unless the alt implementation defines a group structure that's mostly
compatible with the built-in one and supports partially filled group
structures in the same way.

It would be possible to rewrite the SpecifiedECDomain parsing code to avoid
requiring support for partially filled group structures, but that's too
complicated to do now.

Signed-off-by: Gilles Peskine <f805f64266d288fc5467baa7be6cd0ff366f477b@arm.com>

ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls