ASoC: soc-core: export function to find components

Drivers may need to use the ASoC core function to
find out whether a particular component is already
registered with ALSA core or not.
Export the function so that drivers can use it outside
of the file.

Change-Id: I13e4a053de085974b0b53c392a9453e46f1aa66d
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>