[PATCH] testsuite: RISC-V: Fix the typo in param-autovec-mode.c

[PATCH] testsuite: RISC-V: Fix the typo in param-autovec-mode.c

This patch fixes the typo in the test case `param-autovec-mode.c` in the RISC-V
autovec testsuite.

The option `autovec-mode` is changed to `riscv-autovec-mode` to match the
expected parameter name.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/param-autovec-mode.c: Change
	`autovec-mode` to `riscv-autovec-mode` in dg-options.