spi: add support SuperH SPI module

SH7757 has SPI module. This patch supports it.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/README b/README
index e005bc5..37eda11 100644
--- a/README
+++ b/README
@@ -1660,6 +1660,11 @@
 		SPI EEPROM, also an instance works with Crystal A/D and
 		D/As on the SACSng board)
 
+		CONFIG_SH_SPI
+
+		Enables the driver for SPI controller on SuperH. Currently
+		only SH7757 is supported.
+
 		CONFIG_SPI_X
 
 		Enables extended (16-bit) SPI EEPROM addressing.