pulseaudio: fix NEON usage

The NEON intrinsics used by Pulseaudio are only available in either
-mfloat-abi=softfp or -mfloat-abi=hard, not in
-mfloat-abi=soft. Therefore having NEON support in the processor is
not sufficient, we also should *not* be using soft-float.

Moreover, looking at BR2_ARM_ENABLE_NEON to know if the processor has
NEON support is incorrect. This option is only here to allow the user
to tell whether the processor has NEON support or not, for the ARM
cores that only have optional NEON support. Instead, the
BR2_ARM_CPU_HAS_NEON option really indicates whether NEON is available
or not (it is either set automatically by the ARM cores that always
have NEON support, or when BR2_ARM_ENABLE_NEON is enabled by the user
to confirm that his ARM processor has NEON support).

This fixes build failures such as
http://autobuild.buildroot.org/results/675/675c96059be348b594cc92980bef391126931c83/build-end.log



[Peter: add comment about reason for soft abi check]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>