Revert "riscv: kdump: fix crashkernel reserving problem on RISC-V"

This reverts commit 1d6cd214 which was
mistakenly added into v6.6.y and the commit corresponding to the 'Fixes:'
tag is invalid. For more information, see link [1].

This will result in the loss of Crashkernel data in /proc/iomem, and kdump
failed:

```
Memory for crashkernel is not reserved
Please reserve memory by passing"crashkernel=Y@X" parameter to kernel
Then try to loading kdump kernel
```

After revert, kdump works fine. Tested on QEMU riscv.

Link: https://lore.kernel.org/linux-riscv/ZSiQRDGLZk7lpakE@MiWiFi-R3L-srv

 [1]
Cc: Baoquan He <bhe@redhat.com>
Cc: Chen Jiahao <chenjiahao16@huawei.com>
Signed-off-by: Mingzheng Xing <xingmingzheng@iscas.ac.cn>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>