ctl: fix returning zero for dimension level 4

ctl: fix returning zero for dimension level 4

In ALSA kernel/userspace interfaces, 'struct snd_ctl_elem_info' has a
'dimension' parameter. This parameter consists of an array with four
elements. Each element represents the number of members in corresponding
dimension level to construct matrix.

In current implementation, a get function, 'snd_ctl_elem_info_get_dimension()'
is hardcoded to return zero to level 4, against actual value. This commit fixes
the bug.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>