ctl: change former APIs as wrapper functions of element set APIs

ctl: change former APIs as wrapper functions of element set APIs

In former commit, userspace library gets some APIs for element set. Some
existed functions can be simple wrappers of them.

This commit changes these APIs as wrapper functions. Additionally, this
commit also adds local variables for identical information of elements.
This modification is important to keep API consistency.

Some old APIs to add an element have id variables with const type
qualifier, while some new APIs to add element set changes the content of
given parameters. This comes from a change in Linux kernel 4.1.

In this commit [1], in-kernel implementation fills all fields of identical
data in userspace. As a result, when adding a new element set, userspace
applications can get an identical data for the first element in the set.
This lost the semantics of const type qualifier in userspace.

[1] http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/core?id=cab2ed7474bffafd2a68a885e03b85526194abcd

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