Subroutines in power functions may fail. So propagate failures from
subroutines back to the caller of power function with appropriate error
code in return value.
Function polling_with_timeout() returns last value from polled register
on failure and zero on success. So return -ETIMEDOUT on error from power
functions like it is doing Marvell comphy-cp110 driver.
Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I6c709c0c9616ab26829616a42a85b713f314b201