ACPI: video_device_list corruption

The ->cap fields of struct acpi_video_device and struct acpi_video_bus
are 1B each, not 4B. The oversized memset()'s corrupted the subsequent
list_head fields. This resulted in silent corruption without
CONFIG_DEBUG_LIST and BUG's with it. This patch uses sizeof() to pass
the proper bounds to the memset() calls and thereby correct the bugs.

Signed-off-by: William Irwin <wli@holomorphy.com>
Acked-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Len Brown <len.brown@intel.com>