[RISCV] Fix copy/paste mistake in Sh3Add_UWPat. (#161923)
This pattern is a copy of the pattern in Sh3AddPat but using
sh3add.uw instead of sh3add. This is a mistake and the pattern
should be the equivalent of the first pattern from Sh1Add_UWPat and
Sh2Add_UWPat.
These classes were created to share with Andes in a788a1abd9c88, but
there was so many test changes in there that we must have overlooked the
changes to Zba codegen.
