Pad DISPB2_SER_RS has no function DISP1_EXT_CLK.
The definition is obviusly a copy/paste error from
MX51_PAD_DISPB2_SER_RS__DISP1_PIN16.
Signed-off-by: NLothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>