net: ipa: add "gsi_v3.5.1.c"

The next patch adds a GSI register field that is only valid starting
at IPA v3.5.1.  Create "gsi_v3.5.1.c" from "gsi_v3.1.c", changing
only the name of the public regs structure it defines.

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