qcom_gps: Move loc_api_glue_init call to qcom_gps.c

loc_api_glue_init is qcom-specific, so it should not
be in gps.c.
gps: Allow NULL to be passed to ril_update_network_state

strdup(NULL) crashes, but some versions of Android may pass
NULL to this function.
qcom_gps: aggregate some ifs in to a single statement in Android.mk
qcom_gps: Request XTRA data when the engine is opened.

Some versions of Android don't automatically download XTRA data,
so request it explicitly at least once.