Missing INSTR_CREATE_madd macro

**Add a pointer to any prior users list discussion.**
Filing the issue request was suggested by @derekbruening during a code review at Google.

**Is your feature request related to a problem? Please describe.**
[instr_create_api.h](https://github.com/DynamoRIO/dynamorio/blob/master/core/ir/aarch64/instr_create_api.h) contains many aarch64 INSTR_CREATE_\ macros, but is missing an INSTR_CREATE_madd macro for the MADD instruction.

**Describe the solution you'd like**
Adding the macro like other aarch64 instructions, something like:
```
#define INSTR_CREATE_madd(dc, Rd, Rn, Rm, Ra) \
instr_create_1dst_3src((dc), OP_madd, (Rd), (Rn), (Rm), (Ra))
```

**Describe alternatives you've considered**
instr_create_1dst_3src can be used, but it is less convenient and inconsistent with other instructions.