alsa-lib: don't pass --with-softfloat

alsa-lib: don't pass --with-softfloat

Passing this option disables the lfloat and ladsp pcm plugins and certain
APIs as explained by:

https://patchwork.ozlabs.org/patch/619527/

But people might want to use these even if they use software floating point,
and the size difference is really minimal, so don't pass this option.

-rwxr-xr-x 1 peko peko 774K Jul  4 18:50 target-orig/usr/lib/libasound.so.2.0.0
-rwxr-xr-x 1 peko peko 709K Jul  4 19:08 target-softfloat/usr/lib/libasound.so.2.0.0

If people don't want the extra pcm plugins then they can simply be disabled
using BR2_PACKAGE_ALSA_LIB_PCM_PLUGINS.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>