riscv: Fix arch_fixup_fdt always failing without /chosen

riscv: Fix arch_fixup_fdt always failing without /chosen

If /chosen was missing, chosen_offset would never get updated with the new
/chosen node. This would cause fdt_setprop_u32 to fail. This patch fixes
this by setting chosen_offset. In addition, log any errors from setting
boot-hartid as well.

Fixes: 5370478d1c7 ("riscv: Add boot hartid to device tree")
Signed-off-by: Sean Anderson <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
Reviewed-by: Rick Chen <[email protected]>
Reviewed-by: Atish Patra <[email protected]>