arm: improve tests for vqdmladhxq*
gcc/testsuite/ChangeLog:
* gcc.target/arm/mve/intrinsics/vqdmladhxq_m_s16.c: Use
check-function-bodies instead of scan-assembler checks. Use
extern "C" for C++ testing.
* gcc.target/arm/mve/intrinsics/vqdmladhxq_m_s32.c: Likewise.
* gcc.target/arm/mve/intrinsics/vqdmladhxq_m_s8.c: Likewise.
* gcc.target/arm/mve/intrinsics/vqdmladhxq_s16.c: Likewise.
* gcc.target/arm/mve/intrinsics/vqdmladhxq_s32.c: Likewise.
* gcc.target/arm/mve/intrinsics/vqdmladhxq_s8.c: Likewise.