tty/vt: Add missing return value for VT_RESIZE in vt_ioctl()

tty/vt: Add missing return value for VT_RESIZE in vt_ioctl()

In vt_ioctl(), the handler for VT_RESIZE always returns 0, which prevents
users from detecting errors. Add the missing return value so that errors
can be properly reported to users like vt_resizex().

Signed-off-by: Zizhi Wo <wozizhi@huaweicloud.com>
Link: https://lore.kernel.org/r/20250904023955.3892120-1-wozizhi@huaweicloud.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>