USB: xpad: dance pad support

USB: xpad: dance pad support

Adds support for dance pads to the xpad driver. Dance pads require the
d-pad to be mapped to four buttons instead of two axes, so that
combinations of up/down and left/right can be hit simultaneously.
Known dance pads are detected, and there is a module parameter added
to default unknown xpad devices to map the d-pad to buttons if this is
desired. (dpad_to_buttons). Minor modifications were made to port the
changes in the original patch to a newer kernel version.

This patch was originally from Dominic Cerquetti originally written
for kernel 2.6.11.4, with minor modifications (API changes for USB,
spelling fixes to the documentation added in the original patch) made
to apply to the current kernel. I have modified Dominic's original
patch per some suggestions from Dmitry Torokhov. (There was nothing
in the patch format description about multiple From: lines, so I
haven't added myself.)

[akpm@osdl.org: cleanups]
Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>