vt: fix memory overlapping when deleting chars in the buffer

In the Linux kernel, the following vulnerability has been resolved:

vt: fix memory overlapping when deleting chars in the buffer

A memory overlapping copy occurs when deleting a long line. This memory

overlapping copy can cause data corruption when scr_memcpyw is optimized

to memcpy because memcpy does not ensure its behavior if the destination

buffer overlaps with the source buffer. The line buffer is not always

broken, because the memcpy utilizes the hardware acceleration, whose

result is not deterministic.

Fix this problem by using replacing the scr_memcpyw with scr_memmovew.