staging: ccree: fix hash naming convention

The hash files were using a naming convention which was inconsistent
(ssi vs. cc), included a useless prefix (ssi_hash) and often used too
long function names producing monster such as
ssi_ahash_get_initial_digest_len_sram_addr() that made the call site
hard to read.

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

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