avutil: use EINVAL instead of -1 for the return code of crypto related init functions

avutil: use EINVAL instead of -1 for the return code of crypto related init functions

These functions return an error typically when the key size is an
incorrect number. AVERROR(EINVAL) is more specific than -1.

Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>