RISCV: handle 64-bit PCREL data relocations

We would previously fail to handle 64-bit PC-relative relocations on
RISCV.  This was exposed by trying to build with
`-fprofile-instr-generate`.

The original changes restricted the relocation handling to the text
segment as the paired relocations are undesirable in at least the debug
and .eh_frame sections.  We now make this explicit to handle the general
case for the data relocations as well.

It would be preferable to use `R_RISCV_n_PCREL` when available to avoid
an extra relocation.

Differential Revision: https://reviews.llvm.org/D127549
Reviewed By: luismarques, MaskRay

Fixes: #55971