media: em28xx: fix control-message timeouts

USB control-message timeouts are specified in milliseconds and should
specifically not vary with CONFIG_HZ.

Fixes: a6c2ba28 ("[PATCH] v4l: 716: support for em28xx board family")
Cc: stable@vger.kernel.org      # 2.6.16
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>