staging: comedi: Allow comedi on ARM

Bernd Porr reports success getting comedi to work on ARM.  He writes:

"""
comedi works nicely on the Raspberry PI. I've compiled the rpi kernel
with comedi enabled and it works with the USBDUX-sigma (need to test the
other boards). With comedirecord running I can plot one channel at 1kHz
without buffer overflow (resulting to 70% load).

So, I guess we just need to add "ARM" to Kconfig in the comedi subdir?

         depends on BROKEN || FRV || M32R || MN10300 || SUPERH || TILE || X86 || ARM

I'm running just now 3.2.27 but also the development kernel compiles
with ARM enabled (haven't tested yet).

/Bernd
"""

Enable the COMEDI config option to be selected for ARM.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Cc: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>