iio: pressure: mpl115: support MPL115A1

mpl115 driver currently supports i2c interface (MPL115A2).
There is also SPI version (MPL115A1).  The difference between them
is only physical transport so we can easily support both while sharing
most of the code.

Split the driver into a core support module and one module each for I2C
and SPI support.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: linux-iio@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/pressure/mpl115.h b/drivers/iio/pressure/mpl115.h
new file mode 100644
index 0000000..01b6527
--- /dev/null
+++ b/drivers/iio/pressure/mpl115.h
@@ -0,0 +1,24 @@
+/*
+ * Freescale MPL115A pressure/temperature sensor
+ *
+ * Copyright (c) 2014 Peter Meerwald <pmeerw@pmeerw.net>
+ * Copyright (c) 2016 Akinobu Mita <akinobu.mita@gmail.com>
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License.  See the file COPYING in the main
+ * directory of this archive for more details.
+ */
+
+#ifndef _MPL115_H_
+#define _MPL115_H_
+
+struct mpl115_ops {
+	int (*init)(struct device *);
+	int (*read)(struct device *, u8);
+	int (*write)(struct device *, u8, u8);
+};
+
+int mpl115_probe(struct device *dev, const char *name,
+			const struct mpl115_ops *ops);
+
+#endif