RISC-V: Update .SAT_TRUNC dump check due to middle-end change

Due to recent middle-end change, update the .SAT_TRUNC expand dump
check from 2 to 4.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/unop/vec_sat_u_trunc-1.c: Adjust
	asm check times from 2 to 4.

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