fix: Remove wrong write in ARM_t2STMDB_UPD instruction

[DarkaMaul]

Fix issue #1587

New output is:

./cstool -d thumb 2DE9F047
 0  2d e9 f0 47  push.w {r4, r5, r6, r7, r8, sb, sl, lr}
        ID: 128 (push)
        op_count: 8
                operands[0].type: REG = r4
                operands[0].access: READ
                operands[1].type: REG = r5
                operands[1].access: READ
                operands[2].type: REG = r6
                operands[2].access: READ
                operands[3].type: REG = r7
                operands[3].access: READ
                operands[4].type: REG = r8
                operands[4].access: READ
                operands[5].type: REG = sb
                operands[5].access: READ
                operands[6].type: REG = sl
                operands[6].access: READ
                operands[7].type: REG = lr
                operands[7].access: READ
        Registers read: sp r4 r5 r6 r7 r8 sb sl lr
        Registers modified: sp
        Groups: thumb2

[aquynh]

merged, thanks!