net: ipa: include declarations in "ipa_gsi.c"

Include "ipa_gsi.h" in "ipa_gsi.c", so the public functions are
defined before they are used in "ipa_gsi.c".  This addresses some
warnings that are reported with a "W=1" build.

Fixes: c3f398b1

 ("soc: qcom: ipa: IPA interface to GSI")
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>