staging: ramster/debug: Use an array to initialize/use debugfs attributes

Use an array to initialize/use debugfs attributes, it makes them
neater as zcache/debug.c does.

Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>