drivers: hv: remove cast from hyperv_die_event

No need to cast a void pointer.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Link: https://lore.kernel.org/r/20200819090510.28995-1-olaf@aepfle.de


Signed-off-by: Wei Liu <wei.liu@kernel.org>