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/freescale/m547xevb/README b/board/freescale/m547xevb/README
index ce7b27b..6b4fbe5 100644
--- a/board/freescale/m547xevb/README
+++ b/board/freescale/m547xevb/README
@@ -24,7 +24,7 @@
 - arch/m68k/cpu/mcf547x_8x/config.mk		config make
 - arch/m68k/cpu/mcf547x_8x/start.S		start up assembly code
 
-- doc/README.m5475evb			This readme file
+- board/freescale/m547xevb/README	This readme file
 
 - drivers/dma/MCD_dmaApi.c		DMA API functions
 - drivers/dma/MCD_tasks.c		DMA Tasks