Convert CONFIG_DA8XX_GPIO to Kconfig

This converts the following to Kconfig:
   CONFIG_DA8XX_GPIO

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/ea20_defconfig b/configs/ea20_defconfig
index 43292a1..ace5fc51 100644
--- a/configs/ea20_defconfig
+++ b/configs/ea20_defconfig
@@ -29,6 +29,7 @@
 CONFIG_CMD_DIAG=y
 CONFIG_CMD_UBI=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y
+CONFIG_DA8XX_GPIO=y
 # CONFIG_MMC is not set
 CONFIG_NAND=y
 CONFIG_NAND_DAVINCI=y