x86: Drop -Wa,--divide

Fix up all the code that is using / to use >> for divisions instead.

Change-Id: I8a6deb0aa090e0df71d90a5509c911b295833cea
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: http://review.coreboot.org/10819
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/cpu/amd/geode_lx/cache_as_ram.inc

@@ -192,7 +192,7 @@ done_cache_as_ram_main:
 	 * copying it back to itself to invalidate the cache */
 
 	push   %edi
-	mov    $(CONFIG_DCACHE_RAM_SIZE/4),%ecx
+	mov    $(CONFIG_DCACHE_RAM_SIZE >> 2),%ecx
 	push   %esi
 	mov    $(CONFIG_DCACHE_RAM_BASE),%edi
 	mov    %edi,%esi