net: ipa: move version test inside ipa_endpoint_program_delay()

IPA version 4.2 has a hardware quirk that affects endpoint delay
mode, so it isn't used there.  Isolate the test that avoids using
delay mode for that version inside ipa_endpoint_program_delay(),
rather than making that check in the caller.

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