Please revert MTK GPS initialisation to 2.3 way

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After upgrading to 2.4 firmware GPS is not initialized properly. in MW 2.3 
everything was OK.

I am not only one with this issue - forum thread: 
http://www.multiwii.com/forum/viewtopic.php?f=18&t=6317

it is initialization for sure, because flashing back MW 2.3 (which initializes 
GPS upon startup) and again MW 2.4 temporarily solves the problem.

I am too green in arduino and your code to try do it myself, but I think that 
for MTK GPS initialization should be very same as in MW 2.3. If it must be a 
dirty hack - let it be, just put it in compiler conditionals (only for those 
with MTK) and everybody will be happy :)

Original issue reported on code.google.com by maciej.l...@gmail.com on 29 Jun 2015 at 10:21