ARM BLX does not set Registers modified

```
test@test ~ $ cstool -d arm B60100FA
0  b60100fa  blx	#0x6e0
	op_count: 1
		operands[0].type: IMM = 0x6e0
	Registers read: pc
	Registers modified: lr
	Groups: call branch_relative arm v5t jump 
```
**pc** register should be also included in Registers modified
