tinyalsa: Add missing handler for SNDRV_CTL_ELEM_TYPE_BYTES values

Change-Id: Ia1ef4d80b32a4ce2c7a3c78af1abb672cdebdf42
Signed-off-by: Vitaly Rodionov <vitaly.rodionov@wolfsonmicro.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>