ASoC: Add args validation in snd_soc_read/write functions

validation of the codec variable passed to the snd_soc_read
and snd_soc_write functions are missing and can lead to DoS
as refered in CVE-2016-6690

Bug:28838221

Change-Id: I5020f77e252bade5e97efb592afb71fe1b18d952
Signed-off-by: Ravi Kumar Siddojigari <rsiddoji@codeaurora.org>