mfd: max77620: Allow building as a module

The driver works fine as a module, so allowing building as such.

Signed-off-by: Aaron Kling <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/Kconfig

···
 	  There are regulators and adc.
 
 config MFD_MAX77620
-	bool "Maxim Semiconductor MAX77620 and MAX20024 PMIC Support"
+	tristate "Maxim Semiconductor MAX77620 and MAX20024 PMIC Support"
 	depends on I2C=y
 	depends on OF
 	select MFD_CORE

drivers/mfd/max77620.c

···
 #include <linux/mfd/core.h>
 #include <linux/mfd/max77620.h>
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
···
 	.id_table = max77620_id,
 };
 builtin_i2c_driver(max77620_driver);
+
+MODULE_DESCRIPTION("Maxim Semiconductor MAX77620 and MAX20024 PMIC Support");
+MODULE_AUTHOR("Laxman Dewangan <[e-mail]>");
+MODULE_LICENSE("GPL");