net: ipa: use a bitmap for defined endpoints

IPA v5.0 supports more than 32 endpoints, so we will be unable to
represent endpoints defined in the configuration data with a 32-bit
value.  To prepare for that, convert the field in the IPA structure
representing defined endpoints to be a Linux bitmap.

Convert loops based on that field into for_each_set_bit() calls over
the new bitmap.  Note that the loop in ipa_endpoint_config() still
assumes there are 32 or fewer endpoints (when comparing against the
available endpoint bit mask); that assumption goes away in the next
patch.

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