mmc: sdhci-of-aspeed: Drop the use of sdhci_pltfm_free()

mmc: sdhci-of-aspeed: Drop the use of sdhci_pltfm_free()

Since the devm_mmc_alloc_host() helper is already in use,
sdhci_pltfm_free() is no longer needed.

Cc: Andrew Jeffery <andrew@codeconstruct.com.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: linux-aspeed@lists.ozlabs.org
Cc: openbmc@lists.ozlabs.org
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://lore.kernel.org/r/117c13ffd2d67a4c7cad980634591c4851f560b5.1749127796.git.zhoubinbin@loongson.cn
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>