Missing load/store categories for some AARCH64 instructions

Some AARCH64 instructions that perform read/write operations are missing their corresponding load/store categories (DR_INSTR_CATEGORY_LOAD, DR_INSTR_CATEGORY_STORE).
For example:
```
13127323 10416044: 7446 ifetch 4 byte(s) @ 0x0000aaaaefe73500 88eb7dac casa %w11 %w12 (%x13)[4byte] -> %w11 (%x13)[4byte]
13127324 10416044: 7446 read 4 byte(s) @ 0x0000115cffc33ba0 by PC 0x0000aaaaefe73500
13127325 10416044: 7446 write 4 byte(s) @ 0x0000115cffc33ba0 by PC 0x0000aaaaefe73500
```
Performs a read and write operation, hence it should have both load and store categories.

However, hacking the view_tool to print the categories for this instructions reveals that only the load category (printed right before the `casa` opcode) is set:
```
13127323 10416044: 7446 ifetch 4 byte(s) @ 0x0000aaaaefe73500 88eb7dac load casa %w11 %w12 (%x13)[4byte] -> %w11 (%x13)[4byte]
13127324 10416044: 7446 read 4 byte(s) @ 0x0000115cffc33ba0 by PC 0x0000aaaaefe73500
13127325 10416044: 7446 write 4 byte(s) @ 0x0000115cffc33ba0 by PC 0x0000aaaaefe73500
```

This is likely a bug in `decode_load_store_category()` in `core/ir/aarch64/codec.c`.

We have not observed this issue in x86 instructions.