net: ipa: move some GSI setup functions

Move gsi_irq_setup() and gsi_ring_setup() so they're defined right
above gsi_setup() where they're called.  This is a trivial movement
of code to prepare for upcoming patches.

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