net: ipa: use a bitmap for set-up endpoints

Replace the 32-bit unsigned used to track endpoints that have
completed setup with a Linux bitmap, to allow an arbitrary number
of endpoints to be represented.

Rework the error handling in ipa_endpoint_init() so the defined
endpoint bitmap is freed if an error occurs early.  Once endpoints
have been initialized, ipa_endpoint_exit() is used to recover if
the set of filtered endpoints is invalid.

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