gps plugin: fix build with newer gpsd

gps plugin: fix build with newer gpsd

gpsd version 3.18 changed the prototype of gps_read(). Make the
gps_read() call depend on GPSD_API_MAJOR_VERSION to fix that.

This fixes build failures like:

gps.c: In function 'cgps_thread':
gps.c:144:11: error: too few arguments to function 'gps_read'
       if (gps_read(&gpsd_conn) == -1) {
		   ^~~~~~~~

(cherry picked from commit 991a6d3fd38c2435d94de3853fda36b3330cf6ab)