drivers/Kconfig: Cleanup Kconfig

- help message should have same intendation on a specific file
- No need of "depends on" if it's already in a relevant if/endif
- either prompt is used, or not, but let's not mix.

Change-Id: Ib75f25dcf2440fd0ba7bde5c95bc1fbece68be07
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>