ALSA: sscape: Use correct format identifier for size_t

The 'size' member of a struct firmware is passed to snd_printk with a
respective format string using the %d identifier. The 'size' member is
of type size_t, but format identifier %d indicates a signed int data
type. This patch replaces the %d format identifier with the correct %zu
format identifier for size_t data types.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>