doc: update reference to README.board

Update reference in files detected by
scripts/documentation-file-ref-check

doc/README.<board>  => board/<board>/README

Files moved in board directory in
commit 702e6014f15b ("doc: cleanup - move board
READMEs into respective board directories")'

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/board/cobra5272/README b/board/cobra5272/README
index ae0f148..1dad7e3 100644
--- a/board/cobra5272/README
+++ b/board/cobra5272/README
@@ -28,7 +28,7 @@
 
 
 Please refer to u-boot README (general info, u-boot-x-x-x/README),
-to u-boot-x-x-x/doc/README.COBRA5272 and
+to u-boot-x-x-x/board/cobra5272/README and
 to the comments in u-boot-x-x-x/include/configs/cobra5272.h
 
 Configuring u-boot is done by commenting/uncommenting preprocessor defines.