Currently, double precision math functions in newlib/libm/machine/arm detect whether neon instructions can be used for double precision computation by checking the architecture version (>= 8) and the availability of floating-point instructions. However, these instructions would not be available if targeting fpv5-sp-d16 as the FPU, which by definition does not have 64bit float instructions. This patch adds a check that __ARM_FP advertises 64bit float instructions.
* libm/machine/arm/s_ceil.c: Also check that 64bit FP instructions are
available in the guard.
* libm/machine/arm/s_floor.c: Likewise.
* libm/machine/arm/s_nearbyint.c: Likewise.
* libm/machine/arm/s_rint.c: Likewise.
* libm/machine/arm/s_round.c: Likewise.
* libm/machine/arm/s_trunc.c: Likewise.