RISC-V: Make stack_save_restore_2 more robust

RISC-V: Make stack_save_restore_2 more robust

GCC recently changed to emit __riscv_restore_5 which causes this
testcase to fail.
This patch updates the regex to be more robust to change by accepting
any number after __riscv_save_ and __riscv_restore_.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/stack_save_restore_2.c: Accept any number
	after __riscv_save_ and __riscv_restore_.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>