[RISC-V][PR target/118934] Fix ICE in RISC-V long branch support

[RISC-V][PR target/118934] Fix ICE in RISC-V long branch support

I'm not sure if I goof'd this or if I merely upstreamed someone else's goof.
Either way the long branch code isn't working correctly.

We were using 'n' as the output modifier to negate the condition.  But 'n' has
a special meaning elsewhere, so when presented with a condition rather than
what was expected, boom, the compiler ICE'd.

Thankfully there's only a few places where we were using %n which I turned into
%r.

The BZ entry includes a good testcase, it just takes a long time to compile as
it's trying to create the out-of-range scenario.  I'm not including the
testcase due to how long it takes, but I did test it locally to ensure it's
working properly now.

I'm sure that with a little bit of work I could create at testcase that worked
before and fails with the trunk (by taking advantage of the fuzzyness in length
computations).  So I'm going to consider this a regression.

Will push to the trunk after pre-commit testing does its thing.

	PR target/118934
gcc/
	* config/riscv/corev.md (cv_branch): Adjust output template.
	(branch): Likewise.
	* config/riscv/riscv.md (branch): Likewise.
	* config/riscv/riscv.cc (riscv_asm_output_opcode): Handle 'r' rather
	than 'n'.