phy: fix wrong return value of phy framework APIs

Currently, a few APIs (init, exit, power_on, power_off,
suspend, resume) in the phy framework, return a wrong
value (-ENOTSUPP).
This change fixes the return value to be 0, to indicate
there is no actual error.

Change-Id: Ieff05a11738b9d3ec21f171e763c52638de88c8b
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>