net: ipa: simplify ipa_endpoint_program()

Have functions that write endpoint configuration registers return
immediately if they are not valid for the direction of transfer for
the endpoint.  This allows most of the calls in ipa_endpoint_program()
to be made unconditionally.  Reorder the register writes to match
the order of their definition (based on offset).

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