net: ipa: remove two unused register definitions

We do not support inter-EE channel or event ring commands.  Inter-EE
interrupts are disabled (and never re-enabled) for all channels and
event rings, so we have no need for the GSI registers that clear
those interrupt conditions.  So remove their definitions.

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