PM / OPP: predictable fail results for opp_find* functions

Currently the opp_find* functions return -ENODEV when:
a) it cant find a device (e.g. request for an OPP search on device which was not registered)
b) When it cant find a match for the search strategy used

This makes life a little in-efficient for users such as devfreq to make reasonable judgement before switching search strategies.

So, standardize the return results as following:
-EINVAL for bad pointer parameters
-ENODEV when device cannot be found
-ERANGE when search fails

This has the following benefit for devfreq implementation:

Current code:
opp = opp_find_freq_floor(dev, freq);
/* Following search triggers even for un-registered device */ if (opp == ERR_PTR(-ENODEV))

	opp = opp_find_freq_ceil(dev, freq);

Vs (after this change):
opp = opp_find_freq_floor(dev, freq);
/* Will only be triggered if search logic fails: intended usage */ if (opp == ERR_PTR(-ERANGE))

	opp = opp_find_freq_ceil(dev, freq);

Cc MyungJoo Ham <[email protected]>

Cc Kyungmin Park <[email protected]>

Cc "Rafael J. Wysocki" <[email protected]>

Cc Kevin Hilman <[email protected]>

Cc [email protected]

Cc [email protected]

Signed-off-by Nishanth Menon <[email protected]>