spi.h: Rename the spi.h to spi-generic.h

Since there are and will be other files in nb/sb folders, we change
the general spi.h to a file name which is not easy to be duplicated.

Change-Id: I6548a81206caa608369be044747bde31e2b08d1a
Signed-off-by: Zheng Bao <zheng.bao@amd.com>
Signed-off-by: zbao <fishbaozi@gmail.com>
Reviewed-on: http://review.coreboot.org/2309
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
diff --git a/src/drivers/spi/spi_flash.c b/src/drivers/spi/spi_flash.c
index 6b658f8..d1a9504 100644
--- a/src/drivers/spi/spi_flash.c
+++ b/src/drivers/spi/spi_flash.c
@@ -9,7 +9,7 @@
 
 #include <stdlib.h>
 #include <string.h>
-#include <spi.h>
+#include <spi-generic.h>
 #include <spi_flash.h>
 #include <delay.h>
 #ifdef __SMM__