HID: Fix the generic Kconfig options

The generic HID driver is obviously not a special driver, so move it
outside of the special drivers menu. Explain the usage and make the
default follow the HID setting. This should simplify migration from
older kernels. While at it, remove the redundant HID_SUPPORT option
and modify the HID and USB_HID entries to better explain the bus
structure.

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>