req command incorrectly displays the bits for an EC key

When the "req" command is used to generate a new EC key using the -newkey
option it will incorrectly display:

 Generating a 2048 bit EC private key

This commit fixes the message to not display the bit length for EC keys
because we don't currently support getting that during generation.

GitHub Issue #1068

Reviewed-by: Richard Levitte <levitte@openssl.org>