ASoC: davinci-i2s.c: use devm_ functions

The various devm_ functions allocate memory that is released when a driver
detaches.  This patch uses devm_kzalloc, devm_request_mem_region and
devm_ioremap for data that is allocated in the probe function of a platform
device and is only freed in the remove function.

In this case, the original code did not contain a call to iounmap, nor does
one appear anywhere else in the file.  I have assumed that it is safe to
use devm_ioremap for the allocation in any case.

Signed-off-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>