Fix the pagesize argument parsing

Change-Id: I8a3d1a2a70c5ad972d3e150b320ee2184c9d5b4a
diff --git a/mkbootimg/mkbootimg.c b/mkbootimg/mkbootimg.c
index 47ab5f1..a94cb9c 100644
--- a/mkbootimg/mkbootimg.c
+++ b/mkbootimg/mkbootimg.c
@@ -121,8 +121,6 @@
     hdr.second_addr =  0x10F00000;
     hdr.tags_addr =    0x10000100;
 
-    hdr.page_size = pagesize;
-
     while(argc > 0){
         char *arg = argv[0];
         char *val = argv[1];
@@ -159,6 +157,8 @@
             return usage();
         }
     }
+    hdr.page_size = pagesize;
+
 
     if(bootimg == 0) {
         fprintf(stderr,"error: no output filename specified\n");