mmc: atmel: Use devm_mmc_alloc_host() helper

mmc: atmel: Use devm_mmc_alloc_host() helper

Use new function devm_mmc_alloc_host() to simplify the code.

Cc: Aubin Constans <aubin.constans@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Acked-by: Aubin Constans <aubin.constans@microchip.com>
Link: https://lore.kernel.org/r/0688b77b93d27bd2f2e155fca6f53a1766fc3a80.1748933789.git.zhoubinbin@loongson.cn
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>