arch: riscv: stacktrace: undo the fp/sp alignment check in #76045

The change of alignment check in #76045 could be wrong and
isn't unnecessary to fix the stack traces output, undo it for
now.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>