asoc: codecs: wcd938x: limit buffer copy to max buffer size

Check for max buffer size before filling the buffer and
add error handling for cases where buffer copy fails.

Change-Id: I0eede1e5baf63c35c65a704c8bf53c85fe49892e
Signed-off-by: Karthikeyan Mani <kmani@codeaurora.org>