thermocouple: Add initial support for common SPI temperature sensing chips

Signed-off-by: Petri Honkala <cruwaller@gmail.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/spicmds.h

@@ -0,0 +1,10 @@
+#ifndef __SPICMDS_H
+#define __SPICMDS_H
+
+#include <stdint.h> // uint8_t
+
+struct spidev_s *spidev_oid_lookup(uint8_t oid);
+void spidev_transfer(struct spidev_s *spi, uint8_t receive_data
+                     , uint8_t data_len, uint8_t *data);
+
+#endif // stepper.h