vaddr: always check misalign in vaddr_read/write

[happy-lx]

Because when NEMU is running alone and virtual-to-physical address translation is not enabled, if an unaligned memory access occurs, the unaligned exception will not be reported, resulting in inconsistencies with spike's diff.

[cebarobot]

@Ziyue-Zhang, Please consider leaving the PR for the author to merge. There are other people on the reviewer list.