net: ipa: replace ipa->suspend_ref with a flag bit

We take a clock reference in ipa_config() in order to prevent the
the IPA clock from being shutdown until a power management suspend
request arrives.  An atomic field in the IPA structure records
whether that extra reference had been taken.

Rather than using an atomic to represent a Boolean value, define
a new flags bitmap, and define a "clock held" flag to represent
whether the extra clock reference has been taken.

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