ASoC: Fix warning with make xmldocs caused by soc-devres.c

This patch fix warning while "make xmldocs".

Warning(.//sound/soc/soc-devres.c:70): No description
 found for parameter 'platform_drv'
Warning(.//sound/soc/soc-devres.c:70): Excess function
 parameter 'platform' description in 'devm_snd_soc_register_platform'

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>