net: ipa: explicitly disable HOLB drop during setup

During setup, ipa_endpoint_program() programs each endpoint with
various configuration parameters.  One of those registers defines
whether to drop packets when a head-of-line blocking condition is
detected on an RX endpoint.  We currently assume this is disabled;
instead, explicitly set it to be disabled.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>