lib: remove FLASHMAP_OFFSET config variable

The FLASHMAP_OFFSET config variable is used in lib/fmap.c, however
the fmdtool creates a fmap_config.h with a FMAP_OFFSET #define.
Those 2 values are not consistent. Therefore, remove the Kconfig
variable and defer to the #define generated by fmdtool.

Change-Id: Ib4ecbc429e142b3e250106eea59fea1caa222917
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14765
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Leroy P Leahy <leroy.p.leahy@intel.com>

Documentation/Intel/Board/board.html

@@ -65,7 +65,6 @@
   <li>Configure coreboot build:
     <ol type="A">
       <li>Set LOCALVERSION</li>
-      <li>FLASHMAP_OFFSET = 0x00700000</li>
       <li>Select vendor for the board</li>
       <li>Select the board</li>
       <li>CBFS_SIZE = 0x00100000</li>
@@ -238,4 +237,4 @@
 <hr>
 <p>Modified: 20 February 2016</p>
   </body>
-</html>
+</html>