Move variant-specific lines back to variant

[fifieldt]

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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