fbdev: auo_k190x: Use zeroing memory allocator instead of allocator/memset

Use vzalloc for allocating zeroed memory and remove unnecessary
memset function.

Done using Coccinelle.
Generated-by scripts/coccinelle/api/alloc/kzalloc-simple.cocci.
0-day tested with no failures.

Suggested-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
[b.zolnierkie: fixed minor issues in the patch description]
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>