ARM: dts: am335x-icev2: Remove the duplicated pinmux setting

There is no mmc sd card detect on am335x-ice board. But the spi0_cs1
pin being configured as mmcsd_cd. Removing it fixes the below warning
during boot:

pinctrl-single 44e10800.pinmux: pin 44e10960.0 already
requested by 48030000.spi; cannot claim for 48060000.mmc

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
[tony@atomide.com: tidied up commit message]
Signed-off-by: Tony Lindgren <tony@atomide.com>