[RISCV] Use arithmetic for select c, 0, simm12 even with zicond (#156957)

The arithmetic expansion requires fewer registers, and is often fewer
instructions. The critical path does increase by (up to) one
instruction.

This is a sub-case of the expansion we do without zicond, but restricted
specifically to the simm12 case. In the general case where the other
source is a register using zicond is likely better. (Edit: While
technically true, this is a bit misleading, we do this in
combineSelectToBinOp which is also used in the zicond path, just further
down.)

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