NFC: Add basic NCI over SPI

The NFC Forum defines a transport interface based on
Serial Peripheral Interface (SPI) for the NFC Controller
Interface (NCI).

This module implements the SPI transport of NCI, calling SPI module
directly to read/write data to NFC controller (NFCC).

NFCC driver should provide functions performing device open and close.
It should also provide functions asserting/de-asserting interruption
to prevent TX/RX race conditions.
NFCC driver can also fix a delay between transactions if needed by
the hardware.

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/net/nfc/nci/Makefile b/net/nfc/nci/Makefile
index cdb3a2e..7aeedc4 100644
--- a/net/nfc/nci/Makefile
+++ b/net/nfc/nci/Makefile
@@ -4,4 +4,6 @@
 
 obj-$(CONFIG_NFC_NCI) += nci.o
 
-nci-objs := core.o data.o lib.o ntf.o rsp.o
\ No newline at end of file
+nci-objs := core.o data.o lib.o ntf.o rsp.o
+
+nci-$(CONFIG_NFC_NCI_SPI) += spi.o