net: ipa: move IPA flags field

The ipa->flags field is only ever used in "ipa_clock.c", related to
suspend/resume activity.

Move the definition of the ipa_flag enumerated type to "ipa_clock.c".
And move the flags field from the ipa structure and to the ipa_clock
structure.  Rename the type and its values to include "power" or
"POWER" in the name.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>