Fix the offset passed into 'google,board-rev-map'

We were accidentally passing in the offset for 'google,board-rev-map'
as the offset from right after the "params" field.  This is a little
awkward, so instead change it to calculate based on the start of the
machine parameters.

BRANCH=pit
BUG=chrome-os-partner:23024
TEST=With other CLs, SPL can now find the proper revision

Change-Id: I105dc2a8c5f2c3b6d673fb83bdb8ea1f36386c65
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/173238
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
diff --git a/host/lib/exynos.py b/host/lib/exynos.py
index 340f029..33903f8 100644
--- a/host/lib/exynos.py
+++ b/host/lib/exynos.py
@@ -111,15 +111,6 @@
                      (size, pos, size, len(self._spl_data)
                       - pos, len(self._spl_data)))
 
-    # Move past the header and read the parameter list, which is terminated
-    # with \0.
-    pos += 12
-    param_list = struct.unpack('<%ds' % (len(self._spl_data) - pos),
-                               self._spl_data[pos:])[0]
-    param_len = param_list.find('\0')
-    param_list = param_list[:param_len]
-    pos += (param_len + 4) & ~3
-
     #
     # A dictionary of functions processing machine parameters. This is being
     # introduced after more than 20 parameters have been already defined and
@@ -147,6 +138,15 @@
       't': [self._MpRevMap, pos]
       }
 
+    # Move past the header and read the parameter list, which is terminated
+    # with \0.
+    pos += 12
+    param_list = struct.unpack('<%ds' % (len(self._spl_data) - pos),
+                               self._spl_data[pos:])[0]
+    param_len = param_list.find('\0')
+    param_list = param_list[:param_len]
+    pos += (param_len + 4) & ~3
+
     # Use this to detect a missing value from the fdt.
     not_given = 'not-given-invalid-value'