drivers/video/via/ioctl.c: prevent reading uninitialized stack memory

drivers/video/via/ioctl.c: prevent reading uninitialized stack memory

commit b4aaa78f4c2f9cde2f335b14f4ca30b01f9651ca upstream.

The VIAFB_GET_INFO device ioctl allows unprivileged users to read 246
bytes of uninitialized stack memory, because the "reserved" member of
the viafb_ioctl_info struct declared on the stack is not altered or
zeroed before being copied back to the user.  This patch takes care of
it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>