Currently the debug region size is set to 0x100, but according to
FE310-G000 and FE310-G002 manuals:

  FE310-G000: 0x100 - 0xFFF
  FE310-G002: 0x0   - 0xFFF

Change the size to 0x1000 that applies to both.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <1594891856-15474-1-git-send-email-bmeng.cn@gmail.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>