staging: ramster: depends on NET

ramster uses network interfaces that are only present when
CONFIG_NET is enabled, so it should depend on NET.

Fixes these build errors:

drivers/built-in.o: In function `sc_kref_release':
tcp.c:(.text+0x24b9af): undefined reference to `sock_release'
drivers/built-in.o: In function `r2net_open_listening_sock':
tcp.c:(.text+0x24ca2b): undefined reference to `sock_create'
tcp.c:(.text+0x24cb91): undefined reference to `sock_release'
drivers/built-in.o: In function `r2net_recv_tcp_msg':
tcp.c:(.text+0x24cdbd): undefined reference to `sock_recvmsg'
drivers/built-in.o: In function `r2net_send_tcp_msg':
tcp.c:(.text+0x24d341): undefined reference to `sock_sendmsg'
drivers/built-in.o: In function `r2net_start_connect':
tcp.c:(.text+0x24d8fa): undefined reference to `sock_create'
drivers/built-in.o: In function `r2net_shutdown_sc':
tcp.c:(.text+0x24e30c): undefined reference to `kernel_sock_shutdown'
drivers/built-in.o: In function `r2net_accept_one':
tcp.c:(.text+0x24f392): undefined reference to `sock_create_lite'
tcp.c:(.text+0x24f3c3): undefined reference to `sock_release'
drivers/built-in.o: In function `r2net_stop_listening':
(.text+0x250f63): undefined reference to `sock_release'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: konrad.wilk@oracle.com
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>