[RISCV] Make XFAIL test UNSUPPORTED. (#168525)

Currently the test cfi-multiple-location.mir is marked as XFAIL. This
causes failures on some build bots because the test unexpectedly passes.

Mark this test as UNSUPPORTED for now. Later I plan to merge an MR which
fixes an issue in CFIInstrInserter and this test will be enabled.

Author: mgudim

llvm/test/CodeGen/RISCV/cfi-multiple-locations.mir

@@ -1,7 +1,7 @@
 # RUN: llc %s -mtriple=riscv64 \
 # RUN: -run-pass=cfi-instr-inserter \
 # RUN: -riscv-enable-cfi-instr-inserter=true
-# XFAIL: *
+# UNSUPPORTED: target={{.*}}
 
 # Technically, it is possible that a callee-saved register is saved in multiple different locations.
 # CFIInstrInserter should handle this, but currently it does not.