RISC-V: Add xfail test case for wv insn highest overlap

RISC-V: Add xfail test case for wv insn highest overlap

We reverted below patch for wv insn overlap, add the related wv
insn test and mark it as xfail.  And we will remove the xfail
after we support the register overlap in GCC-15.

7e854b58084 RISC-V: Support highest overlap for wv instructions

The below test suites are passed.
* The rv64gcv fully regression test.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/costmodel/riscv/rvv/dynamic-lmul8-11.c: Xfail csr check.
	* gcc.target/riscv/rvv/base/pr112431-39.c: New test.
	* gcc.target/riscv/rvv/base/pr112431-40.c: New test.
	* gcc.target/riscv/rvv/base/pr112431-41.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>