riscv: export kaslr offset and satp in VMCOREINFO ELF notes

The following options are required by the kdump crash utility for RISC-V
based vmcore file:

- kaslr: If the vmcore is generated from a KASLR-enabled Linux kernel,
         the KASLR offset is required for the crash utility to load
         the vmcore. Without the proper kaslr option, the crash utility
         fails to load the vmcore file.
- satp: The exact root page table address helps determine the correct base
        PGD address.

With this patch, RISC-V VMCOREINFO ELF notes now include both kaslr
and satp information.

Signed-off-by: Austin Kim <austin.kim@lge.com>
Link: https://patch.msgid.link/aYwKUE3ZzN7/ZY/A@adminpc-PowerEdge-R7525
Signed-off-by: Paul Walmsley <pjw@kernel.org>