net: ipa: support IPA interrupt addresses for IPA v4.7

Starting with IPA v4.7, registers related to IPA interrupts are
located at a fixed offset 0x1000 above than the addresses used for
earlier versions.  Define and use functions to provide the offset to
use for these registers based on IPA version.

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