Fix non-DER length encoding in two X.509 CRT parsing tests
Fix non-DER length encoding in two X.509 CRT parsing tests

Lengths below 128 Bytes must be encoded as a single 'XX' byte in DER,
but two tests in the X.509 CRT parsing suite used the BER but non-DER
encoding '81 XX' (the first byte 10000001 indicating that the length
is to follow (high bit) and has length 1 byte (low bit)).

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