riscv: dts: microchip: drop duplicated MMC/SDHC node

riscv: dts: microchip: drop duplicated MMC/SDHC node

[ Upstream commit 42a57a47bb0c0f531321a7001972a3ca121409bd ]

Devicetree source is a description of hardware and hardware has only one
block @20008000 which can be configured either as eMMC or SDHC.  Having
two node for different modes is an obscure, unusual and confusing way to
configure it.  Instead the board file is supposed to customize the block
to its needs, e.g. to SDHC mode.

This fixes dtbs_check warning:
  arch/riscv/boot/dts/microchip/microchip-mpfs-icicle-kit.dt.yaml: sdhc@20008000: $nodename:0: 'sdhc@20008000' does not match '^mmc(@.*)?$'

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>