ASoC: Davinci: Use resource_size() helper function

This patch modifies the Davinci i2s and mcasp drivers
to make use of the resource_size() helper function for readability.

Signed-off-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>