mmc: s3cmci: include GPIO descriptor consumer header

The driver uses GPIO Descriptor Consumer Interface so include proper
header to fix compile test errors like:

    drivers/mmc/host/s3cmci.c: In function ‘s3cmci_check_sdio_irq’:
    drivers/mmc/host/s3cmci.c:304:7: error:
        implicit declaration of function ‘gpiod_get_value’; did you mean ‘gpio_get_value’? [-Werror=implicit-function-declaration]

    drivers/mmc/host/s3cmci.c: In function ‘s3cmci_probe_pdata’:
    drivers/mmc/host/s3cmci.c:1451:19: error:
        implicit declaration of function ‘devm_gpiod_get_index’ [-Werror=implicit-function-declaration]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201026153810.89512-1-krzk@kernel.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/s3cmci.c

@@ -17,7 +17,7 @@
 #include <linux/cpufreq.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
-#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/io.h>