staging: fpga manager: framework core

Supports standard ops for low level FPGA drivers.
Various manufacturors' FPGAs can be supported by adding low
level drivers.  Each driver needs to register its ops
using fpga_mgr_register().

Exports methods of doing operations to program  FPGAs. These
should be sufficient for individual drivers to request FPGA
programming directly if desired.

Adds a sysfs interface.  The sysfs interface can be compiled out
where desired in production builds.

Resume is supported by calling low level driver's resume
function, then reloading the firmware image.

The following are exported as GPL:
* fpga_mgr_reset
   Reset the FGPA.

* fpga_mgr_write
   Write a image (in buffer) to the FPGA.

* fpga_mgr_firmware_write
   Request firmware by file name and write it to the FPGA.

* fpga_mgr_name
   Get name of FPGA manager.

* fpga_mgr_state
   Get a state of framework as a string.

* fpga_mgr_register and fpga_mgr_remove
   Register/unregister low level fpga manager driver.

The following sysfs files are created:
* /sys/class/fpga_manager/<fpga>/name
  Name of low level driver.

* /sys/class/fpga_manager/<fpga>/firmware
  Name of FPGA image file to load using firmware class.
  $ echo image.rbf > /sys/class/fpga_manager/<fpga>/firmware

  read: read back name of image file previous loaded
  $ cat /sys/class/fpga_manager/<fpga>/firmware

* /sys/class/fpga_manager/<fpga>/reset
  reset the FPGA
  $ echo 1 > /sys/class/fpga_manager/<fpga>/reset

* /sys/class/fpga_manager/<fpga>/state
  State of fpga framework state machine

Signed-off-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>