sim: pad images to alignment

Adjust the image sizes up to a multiple of 8.  With the strict checking
in the flash driver, we aren't allowed to write partial lines.
diff --git a/sim/src/main.rs b/sim/src/main.rs
index 533e651..27474c8 100644
--- a/sim/src/main.rs
+++ b/sim/src/main.rs
@@ -121,10 +121,12 @@
     // println!("Areas: {:#?}", areadesc.get_c());
 
     // Install the boot trailer signature, so that the code will start an upgrade.
-    let primary = install_image(&mut flash, 0x020000, 32779);
+    // TODO: This must be a multiple of flash alignment, add support for an image that is smaller,
+    // and just gets padded.
+    let primary = install_image(&mut flash, 0x020000, 32784);
 
     // Install an upgrade image.
-    let upgrade = install_image(&mut flash, 0x040000, 41922);
+    let upgrade = install_image(&mut flash, 0x040000, 41928);
 
     // Set an alignment, and position the magic value.
     c::set_sim_flash_align(align);