net: ipa: don't define endpoints unnecessarily

We don't typically need much information about modem endpoints.
Normally we need to specify information about modem endpoints in
configuration data in only two cases:
  - When a modem TX endpoint supports filtering
  - When another endpoint's configuration refers to it

For the first case, the AP initializes the filter table, and must
know how many endpoints (AP and modem) support filtering.  An
example of the second case is the AP->modem TX endpoint, which
defines the modem<-AP RX endpoint as its status endpoint.

There is one exception to this, and it's due to a hardware quirk.
For IPA v4.2 (only) there is a problem related to allocating GSI
channels.  And to work around this, the AP allocates *all* GSI
channels at startup time--including those used by the modem.

Get rid of the configuration information for two endpoints not
required for the SDM845.  SC7180 runs IPA v4.2, so we can't
eliminate any modem endpoint definitions there.

Two more minor changes:
  - Reorder the members defined for the ipa_endpoint_name enumerated
    type to match the order used in configuration data files when
    defining endpoints.
  - Add a new name, IPA_ENDPOINT_MODEM_DL_NLO_TX, which can be used
    for IPA v4.5+.

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