Adds a setting to specify the max length of key press macros that the
device supports.
Setting MacroLength to 1 means that the device supports normal key presses,
(key + modifiers) but not multi key press macros.
0 can be used to indicate that buttons cannot be set as keys at all.
The steelseries driver used some hardcoded values for as the
only supported device was the rival 310. This moves that data
to the .device file.
The default resolutions used are changed from hardcoded 1000
and 2000, to the two first entries in the dpi list. Picking
actual values from the specified dpi list or range is safer.
The driver does not yet support button mappings or any
non-solid LED modes.
The device does not support reading out the current
configuration. On probe some default values are used
to get a usable profile.
