[llvm] [RISCV] Place mergeable small read only data into srodata section (PR #82214)

[Kito Cheng via llvm-commits]

kito-cheng wrote:

> I am still interested in changing the default limit from 8 to 0. Is there interest for GCC to do so?

>From the benchmarking aspect, it's hard to say I am interesting on change the default value honestly, since I didn't got the point about the disadvantage when the GP relaxation is turn off, but it did help when GP relaxation turn on, however I may missed something, so I am happy to discuss this more, and change my mind IF we gather enough arguments :)

|                             | w/ GP relax                        | w/o GP relax |
| ---------------------- | ----------------------------------- | ------------------- |
| Default limit 0   | Less chance on GP relax `*1` | No difference?`*3` |
| Default limit 8   | More chance on GP relax `*2` | No difference |


`*1`: because the range is limited, so same range cover more symbol have a higher winning rate.
`*2`: Compare to `Default limit 0`
`*3`: I guess I may missed something here, so need your input here.

https://github.com/llvm/llvm-project/pull/82214