RISC-V: Fix uninitialized probability for GIMPLE IR tests

RISC-V: Fix uninitialized probability for GIMPLE IR tests

This patch fix unitialized probability in GIMPLE IR code tests:
FAIL: gcc.dg/vect/slp-reduc-10a.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10a.c (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10a.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10a.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10b.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10b.c (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10b.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10b.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10c.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10c.c (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10c.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10c.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10d.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10d.c (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10d.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10d.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10e.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10e.c (test for excess errors)
FAIL: gcc.dg/vect/slp-reduc-10e.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/slp-reduc-10e.c -flto -ffat-lto-objects (test for excess errors)
FAIL: gcc.dg/vect/vect-cond-arith-2.c (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/vect-cond-arith-2.c (test for excess errors)
FAIL: gcc.dg/vect/vect-cond-arith-2.c -flto -ffat-lto-objects (internal compiler error: in compute_probabilities, at config/riscv/riscv-vsetvl.cc:4358)
FAIL: gcc.dg/vect/vect-cond-arith-2.c -flto -ffat-lto-objects (test for excess errors)

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (pass_vsetvl::earliest_fusion): Skip
	never probability.
	(pass_vsetvl::compute_probabilities): Fix unitialized probability.