Cleanup GPS init

[sjkelly]

Fixes up some regressions in the GPS Enable and UART:

sjkelly@pathfinder:~/xtrx_julia/software (sjk/ppscal1=)$ julia --project ./scripts/gps_dump.jl 
[INFO] SoapyXTRX initializing...
[INFO] Opened devnode /dev/litepcie8, serial 134c5241b884854
[INFO] LMS7002M info: revision 1, version 7
[INFO] CGEN tune 80.000000 MHz (fref=26.000000 MHz) begin
[INFO] SoapyXTRX initialization complete
[ Info: Restarting GPS...
[ Info: Enabling GPS...
$PMTK011,MTKGPS*08
$PMTK010,001*2E
$PMTK011,MTKGPS*08
$PMTK010,002*2D
$GNGGA,235943.100,,,,,0,0,,,M,,M,,*5D
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GLGSA,A,1,,,,,,,,,,,,,,,*02
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GNRMC,235943.100,V,,,,,0.00,0.00,050180,,,N*54
$GNVTG,0.00,T,,M,0.00,N,0.00,K,N*2C
$GNGGA,235944.100,,,,,0,0,,,M,,M,,*5A
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GLGSA,A,1,,,,,,,,,,,,,,,*02
$GPGSV,1,1,00*79
$GLGSV,1,1,00*65
$GNRMC,235944.100,V,,,,,0.00,0.00,050180,,,N*53