ipa: Fix MHI flavor detection

The ipa3_get_hw_type_index() uses the ipa3_ctx->ipa_config_is_mhi
for MHI flavor detection. Therefore the ipa3_ctx->ipa_config_is_mhi
has to be initialized before the ipa3_get_hw_type_index() call.

Change-Id: I8446c68f8b1fb0e2a56838e92f59198bd6890462
Signed-off-by: Ilia Lin <ilial@codeaurora.org>