mmc: sdhci-of-sparx5: Drop the use of sdhci_pltfm_free()

mmc: sdhci-of-sparx5: 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: Steen Hegelund <Steen.Hegelund@microchip.com>
Cc: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Acked-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://lore.kernel.org/r/67b5e9076056da66d9fc8951fafd4f48ddd3ca25.1749127796.git.zhoubinbin@loongson.cn
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>