cris-dis: Clean memory allocation

cris-dis: Clean memory allocation

The old code used sizeof(const struct cris_opcode **) where it should
have used sizeof(const struct cris_opcode *). As both sizes give the
same value, the resulting binary was ok, but static code analyzers
like coverity and clang complained.

This is fixed here, and the code is also simplified by using g_new0.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>