mmc: meson-mx-sdio: Fix misuse of GENMASK macro

Arguments are supposed to be ordered high then low.

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Fixes: ed80a13b ("mmc: meson-mx-sdio: Add a driver for the Amlogic
Meson8 and Meson8b SoCs")
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>