Turned on executable bits for obmc_ser_num.

Change-Id: Ic7c556cef39068ea16300d3dcaecebcc0a06700a
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/bin/obmc_ser_num b/bin/obmc_ser_num
old mode 100644
new mode 100755