media: vidtv: Use kmemdup instead of kzalloc and memcpy

Fixes coccicheck warning:
drivers/media/test-drivers/vidtv/vidtv_psi.c:509:10-17: WARNING
opportunity for kmemdup

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>