[RISCV] Use XLenRI alias for RegInfoByHwMode instances

This avoids tedious repetition and matches what we do for the
ValueTypeByHwMode uses.

Reviewed By: craig.topper, luismarques

Differential Revision: https://reviews.llvm.org/D96649

GitOrigin-RevId: 74df1ffaad3937891b808c894cfafe2fa29b1ad6
1 file changed