add vr and sio schedulers

 block/Kconfig.iosched                       |  25 ++
 block/Makefile                              |   2 +
 block/sio-iosched.c                         | 399 ++++++++++++++++++++++++
 block/vr-iosched.c                          | 451 ++++++++++++++++++++++++++++
 5 files changed, 881 insertions(+)
 create mode 100644 block/sio-iosched.c
 create mode 100644 block/vr-iosched.c