RISC-V: Include pattern stmts for dynamic LMUL computation [PR114516].

When scanning for program points, i.e. vector statements, we're missing
pattern statements.  In PR114516 this becomes obvious as we choose
LMUL=8 assuming there are only three statements but the divmod pattern
adds another three.  Those push us beyond four registers so we need to
switch to LMUL=4.

This patch adds pattern statements to the program points which helps
calculate a better register pressure estimate.

	PR target/114516

gcc/ChangeLog:

	* config/riscv/riscv-vector-costs.cc (compute_estimated_lmul):
	Add pattern statements to program points.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/costmodel/riscv/rvv/pr114516.c: New test.