arm64/disassem.c: remove redundant OP_RN_SP for TYPE_02

Removed redundant OP_RN_SP for TYPE_02, since these addressing modes
always use the SP register, never XZR.

Reviewed by: mhorne
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D40588

(cherry picked from commit e57b86266b80e1eed266a8287ae51c941c591b9d)