The Schenker XMG C504 is a rebranded Gigabyte P35 v2 laptop.
Therefore it also needs a keyboard reset to detect the Elantech touchpad.
Otherwise the touchpad appears to be dead.

With this patch the touchpad is detected:

$ dmesg | grep -E "(i8042|Elantech|elantech)"

[    2.675399] i8042: PNP: PS/2 Controller [PNP0303:PS2K,PNP0f13:PS2M] at 0x60,0x64 irq 1,12
[    2.680372] i8042: Attempting to reset device connected to KBD port
[    2.789037] serio: i8042 KBD port at 0x60,0x64 irq 1
[    2.791586] serio: i8042 AUX port at 0x60,0x64 irq 12
[    2.813840] input: AT Translated Set 2 keyboard as /devices/platform/i8042/serio0/input/input4
[    3.811431] psmouse serio1: elantech: assuming hardware version 4 (with firmware version 0x361f0e)
[    3.825424] psmouse serio1: elantech: Synaptics capabilities query result 0x00, 0x15, 0x0f.
[    3.839424] psmouse serio1: elantech: Elan sample query result 03, 58, 74
[    3.911349] input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio1/input/input6
Signed-off-by: Patrick Scheuring <patrick.scheuring.dev@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>