HID: corsair: fix mapping of non-keyboard usages

This fixes a bug where the Volume Up key was ignored because it uses the same usage code as G18. Special Corsair usage codes are in the keyboard page, other pages should be left to the generic driver.

Signed-off-by: Clément Vuchener <clement.vuchener@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>