riscv: Remove 32b kernel mapping from page table dump

The 32b kernel mapping lies in the linear mapping, there is no point in
printing its address in page table dump, so remove this leftover that
comes from moving the kernel mapping outside the linear mapping for 64b
kernel.

Fixes: e9efb21fe352 ("riscv: Prepare ptdump for vm layout dynamic addresses")
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>