cosmetic: README.SPL: fix a typo

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/doc/README.SPL b/doc/README.SPL
index 4e1cb28..ac9a213 100644
--- a/doc/README.SPL
+++ b/doc/README.SPL
@@ -77,7 +77,7 @@
 
 	normal_cpu:spl_cpu
 
-This this case CPU will be set to "normal_cpu" during the main u-boot
+This case CPU will be set to "normal_cpu" during the main u-boot
 build and "spl_cpu" during the SPL build.