Move variant-specific lines back to variant (#6044)

Last release a change introduced different branching functions in
gps.cpp based on the model of a device. This makes the code less
readable and introduces the potential for bugs.

This patch creates a new variable, GPS_PROBETRIES that can be set
in variant.h of devices that will control how many times we will
probe for GPS presence. It sets up the T1000-E to use this variable
and cleans the code in gps.c

variants/tracker-t1000-e/variant.h

@@ -111,6 +111,7 @@ extern "C" {
 #define GPS_TX_PIN PIN_SERIAL1_TX
 
 #define GPS_BAUDRATE 115200
+#define GPS_PROBETRIES 5
 
 #define PIN_GPS_EN (32 + 11) // P1.11
 #define GPS_EN_ACTIVE HIGH