HSI: hsi: Introducing HSI framework

Adds HSI framework in to the linux kernel.

High Speed Synchronous Serial Interface (HSI) is a
serial interface mainly used for connecting application
engines (APE) with cellular modem engines (CMT) in cellular
handsets.

HSI provides multiplexing for up to 16 logical channels,
low-latency and full duplex communication.

Signed-off-by: Carlos Chinea <carlos.chinea@nokia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index b5e6f24..5289508 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@
 
 source "drivers/spi/Kconfig"
 
+source "drivers/hsi/Kconfig"
+
 source "drivers/pps/Kconfig"
 
 source "drivers/ptp/Kconfig"