use -mfpu=auto for arm/simd/vmmla_1.c

use -mfpu=auto for arm/simd/vmmla_1.c

On some of our arm targets, we get various -mfpu flags implicitly or
explicitly passed to the compiler during test runs.  The target
options pushed in arm_neon.h that affect vmmlaq_s32 set isa_bit_neon,
but the caller doesn't have that bit set, so arm_can_inline_p rejects
the attempt to inline it, and the test fails.

An explicit -mfpu=neon would address the compile problem, but cause
the assembler to reject the generated code.

So this patch adds -mfpu=auto to the test, overriding any implicit
flags with the fpu implied by the arch.

for  gcc/testsuite/ChangeLog

	* gcc.target/arm/simd/vmmla_1.c: Pass -mfpu=auto.