mini2440: add U-Boot memory layout

from the start message below, we can draw a rough layout of 64M memory:
U-Boot 2012.07-00006-ga11b47a-dirty (May 04 2013 - 17:03:57)

U-Boot code: 33000000 -> 3302FAB0  BSS: -> 33041530
CPUID: 32440001
FCLK:      405 MHz
HCLK:      135 MHz
PCLK:   67.500 MHz
monitor len: 00041530
ramsize: 04000000
TLB table at: 33ff0000
Top of RAM usable for U-Boot at: 33ff0000
Reserving 261k for U-Boot at: 33fae000
Reserving 4160k for malloc() at: 33b9e000
Reserving 32 Bytes for Board Info at: 33b9dfe0
Reserving 120 Bytes for Global Data at: 33b9df68
New Stack Pointer is: 33b9df58
RAM Configuration:
Bank #0: 30000000 64 MiB
relocation Offset is: 00fae000
WARNING: Caches not enabled
monitor flash len: 000348C8
Now running in RAM - U-Boot at: 33fae000
Flash: *** failed ***

Signed-off-by: Fudong Bai <fudongbai@gmail.com>
mini2440: changed download address

Download u-boot image to 0x33F8_0000 has problem, since the board_init_r
will call mem_malloc_init to clear the memory from 0x33b9_e000 to
0x33fa_dfff, so change to 0x3300_0000 for now

Signed-off-by: Fudong Bai <fudongbai@gmail.com>
mini2440: add TODO list

Signed-off-by: Fudong Bai <fudongbai@gmail.com>
tools: boot_usb: change object name

Signed-off-by: Fudong Bai <fudongbai@gmail.com>