testsuite/arm: Add arm_v8_2a_i8mm options in gcc.target/arm/simd/vmmla_1.c

testsuite/arm: Add arm_v8_2a_i8mm options in gcc.target/arm/simd/vmmla_1.c

We need to add the options corresponding to the arm_v8_2a_i8mm_ok
effective target in order to use the right float-abi option:
-mfloat-abi=softfp makes the test pass for arm-linux-gnueabi,
while no -mfloat-abi option is needed for arm-linux-gnueabihf.

2021-03-19  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/testsuite/
	* gcc.target/arm/simd/vmmla_1.c: Add arm_v8_2a_i8mm options.