arm64: dts: renesas: Switch eMMC bus to 1V8 on Salvator-X and ULCB

The eMMC card has two supplies, VCC and VCCQ. The VCC supplies the NAND
array and the VCCQ supplies the bus. On Salvator-X and ULCB, the VCC is
connected to 3.3V rail, while the VCCQ is connected to 1.8V rail. Adjust
the pinmux to match the bus, which is always operating in 1.8V mode.

While at it, deduplicate the pinmux entries, which are now the same for
both default and UHS modes. We still need the two pinctrl entries to
match the bindings though.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>