ARM64: rockchip_cros_defconfig: Don't force the command line

ARM64: rockchip_cros_defconfig: Don't force the command line

There's no reason to force the command line at this point.

Forcing the command like makes it pretty hard to switch between eMMC and
SD card boots because the old command line forced the root filesystem to
/dev/mmcblk0p3 vs. depthcharge automatically inserting the right UUID
based on where it found the kernel.

BUG=None
TEST=I see my command line now.

Change-Id: I5f76b60b9726aee2152c09fbd6460b2b973b0b20
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>