TYPE_ETRAX_FS_TIMER is a sysbus device, so its DeviceClass::reset()
handler is called automatically when its qbus parent is reset
(we don't need to register it manually).

Convert the generic reset to a enter/hold resettable ones, and
remove the qemu_register_reset() call.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-Id: <20210502163931.552675-2-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>