hw/ufs: Fix incorrect register fields

This patch fixes invalid ufs register fields.
This fixes an issue reported by Bin Meng that
caused ufs to fail over riscv.

Fixes: bc4e68d362ec ("hw/ufs: Initial commit for emulated Universal-Flash-Storage")
Signed-off-by: Jeuk Kim <jeuk20.kim@samsung.com>
Reported-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Tested-by: Bin Meng <bmeng@tinylab.org>