staging: ramster: fix range checks in zcache_autocreate_pool()

If "pool_id" is negative then it leads to a read before the start of the
array.  If "cli_id" is out of bounds then it leads to a NULL dereference
of "cli".  GCC would have warned about that bug except that we
initialized the warning message away.

Also it's better to put the parameter names into the function
declaration in the .h file.  It serves as a kind of documentation.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>