rtc: add support for s35392a

Add support for S35392A RTC. The driver supports both U-Boot driver
models.

Signed-off-by: Nandor Han <nandor.han@ge.com>
Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Cc: Heiko Schocher <hs@denx.de>
diff --git a/lib/Kconfig b/lib/Kconfig
index 18663ba..f447c53 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -80,6 +80,9 @@
 config RBTREE
 	bool
 
+config BITREVERSE
+	bool "Bit reverse library from Linux"
+
 source lib/dhry/Kconfig
 
 menu "Security support"