Sansa AMS bootloader: enter USB mode only when needed

- If an error happens when reading partitions / rockbox.sansa
- If the select button was pressed

add an argument to error() to not power off, when we're going to enter
USB mode to try to fix the problem, but display the error message anyway
for debugging purpose

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@27075 a1c6a512-1295-4272-9138-f99709370657

bootloader/main-pp.c

@@ -540,7 +540,7 @@ void* main(void)
         }
         printf(buf);
     } else {
-        error(EATA, i);
+        error(EATA, i, true);
     }
 #endif
 
@@ -548,7 +548,7 @@ void* main(void)
     num_partitions = disk_mount_all();
     if (num_partitions<=0)
     {
-        error(EDISK,num_partitions);
+        error(EDISK,num_partitions, true);
     }
 
     /* Just list the first 2 partitions since we don't have any devices yet 
@@ -643,7 +643,7 @@ void* main(void)
             return (void*)loadbuffer;
         }
         
-        error(0, 0);
+        error(0, 0, true);
     }
     return (void*)loadbuffer;
 }