goldfish: add QEMU pipe driver

A QEMU pipe is a very fast communication channel between the
guest system and the emulator. Usage from the guest is simply
something like;

  // connect to special device
  fd = open("/dev/qemu_pipe", O_RDWR);

  // tell which service we want to talk to (must be zero-terminated)
  write(fd, "pipeName", strlen("pipeName")+1);

  // do read()/write() through fd now
  ...

  // close channel
  close(fd);

Signed-off-by: David 'Digit' Turner <digit@android.com>
[Added support for parameter buffers for speed]
igned-off-by: Xin, Xiaohui <xiaohui.xin@intel.com>
Signed-off-by: Jiang, Yunhong <yunhong.jiang@intel.com>
Signed-off-by: Nakajima, Jun <jun.nakajima@intel.com>
[Ported to 3.6]
Signed-off-by: Tom Keel <thomas.keel@intel.com>
[Ported to 3.7, moved to platform/goldfish]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>