Add sq, lq, c_ldq

[ViktoriaGromova]

Hello, @herumi!
This small PR adds sq, lq, c_ldq.
Thank you in advance.

[dannykireev]

Hello, @herumi !
Are you planning to merge this PR. I think this functionality might prove useful.
Could you please review?
Thanks in advance.

[herumi]

I have so many tasks, but I am not feeling well. I will do it little by little, so please wait for me.

[herumi]

Thank you for the patch. But sq and lq are for RV128, which is working in progress, and riscv64-linux-gnu-as seems not to support those, so I won't append them until it supports them.

% riscv64-linux-gnu-as -march=rv128 a.s
Assembler messages:
Error: rv128: ISA string must begin with rv32 or rv64
a.s:1: Error: unrecognized opcode `lq x3,512(sp)'

% riscv64-linux-gnu-as -v
GNU assembler version 2.40 (riscv64-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.40

[dannykireev]

@herumi what about adding them under some ifdef for future use?

[herumi]

If the correctness of the code can be verified with Binutils, it is acceptable to add it with ifdef. Do you know of any version to support them?

[dannykireev]

@herumi unfortunately, I couldn't find the proper toolchain to support them. So apparently, we should leave them be, until support is available. Thank you for your feedback!

[herumi]

Okay, I'll close this PR now, and will support it later.
By the way, if you have a list of instructions you want, I'll support it step by step. It will reduce the costs that you make a PR and that I check it. How about it?

[dannykireev]

Hello, @herumi. Sorry for long answer. Thank you for your proposition, that sounds good.