staging: ccree: fix ivgen naming convention

The ivgen files were using a func naming convention which was
inconsistent (ssi vs. cc), included a long prefix (ssi_ivgen)
and often too long.

Make the code more readable by switching to a simpler, consistent naming
convention.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>