openrisc: mm/init.c: remove unused memblock_region variable in map_ram()

Kernel test robot reports:

cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

>> arch/openrisc/mm/init.c:125:10: warning: Uninitialized variable: region [uninitvar]
            region->base, region->base + region->size);
            ^

Replace usage of memblock_region fields with 'start' and 'end' variables
that are initialized in for_each_mem_range() and remove the declaration of
region.

Fixes: b10d6bca ("arch, drivers: replace for_each_membock() with for_each_mem_range()")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

arch/openrisc/mm/init.c

@@ -75,7 +75,6 @@ static void __init map_ram(void)
 	/* These mark extents of read-only kernel pages...
 	 * ...from vmlinux.lds.S
 	 */
-	struct memblock_region *region;
 
 	v = PAGE_OFFSET;
 
@@ -121,7 +120,7 @@ static void __init map_ram(void)
 		}
 
 		printk(KERN_INFO "%s: Memory: 0x%x-0x%x\n", __func__,
-		       region->base, region->base + region->size);
+		       start, end);
 	}
 }