net: ipa: update gsi registers for IPA v4.5

Very few GSI register definitions change for IPA v4.5, however
as a group their position in memory shifts a constant amount
(handled by the next commit).

Add definitions and update comments to the set of GSI registers to
support changes that come with IPA v4.5.

Update the logic in gsi_channel_program() to accommodate the new
(expanded) PREFETCH_MODE field in the CH_C_QOS register.

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