staging: ramster: Move debugfs code out of ramster.c file

Note that at this point there is no CONFIG_RAMSTER_DEBUG
option in the Kconfig. So in effect all of the counters
are nop until that option gets introduced in patch:
ramster/debug: Add CONFIG_RAMSTER_DEBUG Kconfig entry

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>