gpio: add support for 74x164 serial-in/parallel-out 8-bit shift register

Add support for generic 74x164 serial-in/parallel-out 8-bits shift
register.  This driver can be used as a GPIO output expander.

[akpm@linux-foundation.org: remove unused local `refresh']
Signed-off-by: Miguel Gaio <miguel.gaio@efixo.com>
Signed-off-by: Juhos Gabor <juhosg@openwrt.org>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/spi/74x164.h b/include/linux/spi/74x164.h
new file mode 100644
index 0000000..d85c52f
--- /dev/null
+++ b/include/linux/spi/74x164.h
@@ -0,0 +1,11 @@
+#ifndef LINUX_SPI_74X164_H
+#define LINUX_SPI_74X164_H
+
+#define GEN_74X164_DRIVER_NAME "74x164"
+
+struct gen_74x164_chip_platform_data {
+	/* number assigned to the first GPIO */
+	unsigned	base;
+};
+
+#endif