boards.cfg: Fix the comment for invoking tools/reformat.py from vim

Add the missing bang (!) to execute external command, otherwise it does not
work.

Signed-off-by: Axel Lin <axel.lin@ingics.com>

boards.cfg

@@ -38,7 +38,7 @@
 # It can be used from a shell:
 #	tools/reformat.py -i -d '-' -s 8 <boards.cfg >boards0.cfg && mv boards0.cfg boards.cfg
 # It can directly be invoked from vim:
-#	:%tools/reformat.py -i -d '-' -s 8
+#	:%!tools/reformat.py -i -d '-' -s 8
 #
 # Status, Arch, CPU:SPLCPU, SoC, Vendor, Board name, Target, Options, Maintainers
 ###########################################################################################################