spa: clamp required alignment to cpu alignment

pipewire will allocate buffers aligned to the max alignment required for
the CPU. Take this into account and don't expect larger alignment.

Fixes a warning in mixer-dsp when the CPU max alignment is 16 but the
plugin requires 32 bytes alignment for the AVX2 path (that would never
be chosen on the CPU).

See #2074

spa/plugins/audioconvert/resample.c

@@ -48,7 +48,6 @@ static struct spa_log_topic *log_topic = &SPA_LOG_TOPIC(0, "spa.resample");
 #define DEFAULT_RATE		48000
 #define DEFAULT_CHANNELS	2
 
-#define MAX_ALIGN	16
 #define MAX_BUFFERS	32
 
 struct impl;