vt: fix unicode buffer corruption when deleting characters

This is the same issue that was fixed for the VGA text buffer in commit
39cdb68 ("vt: fix memory overlapping when deleting chars in the
buffer"). The cure is also the same i.e. replace memcpy() with memmove()
due to the overlaping buffers.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Fixes: 81732c3 ("tty vt: Fix line garbage in virtual console on command line edition")
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/sn184on2-3p0q-0qrq-0218-895349s4753o@syhkavp.arg
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: npitre

drivers/tty/vt/vt.c

@@ -381,7 +381,7 @@ static void vc_uniscr_delete(struct vc_data *vc, unsigned int nr)
 		u32 *ln = vc->vc_uni_lines[vc->state.y];
 		unsigned int x = vc->state.x, cols = vc->vc_cols;
 
-		memcpy(&ln[x], &ln[x + nr], (cols - x - nr) * sizeof(*ln));
+		memmove(&ln[x], &ln[x + nr], (cols - x - nr) * sizeof(*ln));
 		memset32(&ln[cols - nr], ' ', nr);
 	}
 }