mmc: sdhci_am654: Fix SLOTTYPE write

In the call to regmap_update_bits() for SLOTTYPE, the mask and value
fields are exchanged. Fix this.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Fixes: 41fd4cae ("mmc: sdhci_am654: Add Initial Support for AM654 SDHCI driver")
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>