ctl: add dimension validator

ctl: add dimension validator

Linux 4.7 or former have no validator of dimension information. This can
causes an issue related to user-defined element set. For example, When
calculated total members in multi-dimensional matrix is larger than actual
capacity of snd_ctl_elem_value_t, processes to handle the element can
cause buffer-over-run.

For backward portability of this userspace library, this commit adds a
validator of dimension information. When userspace applications give
invalid dimension information to APIs to add element set, they receive
-EINVAL.

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