ipc: apr_v2: export symbols used by WCD driver

Add EXPORT_SYMBOL to symbols used by codec driver.
Codec driver is built as separate module and requires
symbols called to be exported.

Change-Id: I3d1bc6c8cbfc1b92f790b700ecfeaff211ddcff0
Signed-off-by: Rohit Kumar <rohitkr@codeaurora.org>