NFC: st21nfca: Auto-select core module

The core st21nca module is useless without the I2C access module.
So hide NFC_ST21NFCA and select it automatically if either
NFC_ST21NFCA_I2C is selected.

This avoids presenting NFC_ST21NFCA when NFC_ST21NFCA_I2C can't be
selected.

Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/nfc/st21nfca/Kconfig

 config NFC_ST21NFCA
-	tristate "STMicroelectronics ST21NFCA NFC driver"
-	depends on NFC_HCI
+	tristate
 	select CRC_CCITT
-	default n
 	---help---
 	  STMicroelectronics ST21NFCA core driver. It implements the chipset
 	  HCI logic and hooks into the NFC kernel APIs. Physical layers will
 	  register against it.
 
-	  To compile this driver as a module, choose m here. The module will
-	  be called st21nfca.
-	  Say N if unsure.
-
 config NFC_ST21NFCA_I2C
-	tristate "NFC ST21NFCA i2c support"
-	depends on NFC_ST21NFCA && I2C && NFC_SHDLC
+	tristate "STMicroelectronics ST21NFCA NFC driver (I2C)"
+	depends on NFC_HCI && I2C && NFC_SHDLC
+	select NFC_ST21NFCA
 	---help---
 	  This module adds support for the STMicroelectronics st21nfca i2c interface.
 	  Select this if your platform is using the i2c bus.