drm/gma500: fix memory disclosures due to uninitialized bytes

drm/gma500: fix memory disclosures due to uninitialized bytes

BugLink: https://bugs.launchpad.net/bugs/1858428
[ Upstream commit ec3b7b6eb8c90b52f61adff11b6db7a8db34de19 ]

"clock" may be copied to "best_clock". Initializing best_clock
is not sufficient. The fix initializes clock as well to avoid
memory disclosures and informaiton leaks.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191018044150.1899-1-kjlu@umn.edu
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>