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/calimain_defconfig b/configs/calimain_defconfig
index 7908cfc..bc704ff 100644
--- a/configs/calimain_defconfig
+++ b/configs/calimain_defconfig
@@ -23,6 +23,7 @@
 CONFIG_ENV_IS_IN_FLASH=y
 CONFIG_BOOTCOUNT_LIMIT=y
 CONFIG_SYS_BOOTCOUNT_ADDR=0x01C23000
+CONFIG_DA8XX_GPIO=y
 # CONFIG_MMC is not set
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_SYS_NS16550=y