adl: Set iSpeedType to RPM for get-fanspeed requests

...and ensure we don't change do something weird with the fan when initially setting user-defined speed flag.

Fixes crash on R9 cards. Thanks to tkg for hints on what was wrong!
RPM preferred over percent since writing RPM back is always supported (while percent is not in some cases).

Conflicts:
	adl.c
adl: unambiguosly check if FanSpeedInfo specifies support for either mechanism to set FanSpeed.

Reported by olejr: https://github.com/veox/sgminer/issues/15#issuecomment-32715082

Related issue: https://github.com/veox/sgminer/issues/15