Just to make sure we never have an UUID == 0

   This file was clearly clearly but built.

   This common code can be used byt posix based boars to provide
   the board_identity API.

   The form of the PX4  GUID is as follows:
   offset:0         1         2         -           17
      <ARCH MSD><ARCH LSD><MSD CPU UUID>...<LSD CPU UUID>

   Where <ARCH MSD><ARCH LSD> are a monotonic ordinal number assigned by
   PX4 to a chip architecture (PX4_SOC_ARCH_ID). The 2 bytes are used to
   create a globally unique ID when prepended to a padded CPU ID.

   In the case where the CPU's UUID is shorter than 16 bytes it will be
   padded with 0's starting at offset [2] until
   PX4_CPU_MFGUID_BYTE_LENGTH-PX4_CPU_UUID_BYTE_LENGTH -1
   I.E. For the STM32
   offset:0         1     2  3  4  5  6             -            17
     <ARCH MSD><ARCH LSD>[0][0][0][0]<MSD CPU UUID>...<LSD CPU UUID>

   I.E. For as CPU with a 16 byte UUID
   offset:0         1         2         -           17
     <ARCH MSD><ARCH LSD><MSD CPU UUID>...<LSD CPU UUID>

desired such that it's possible to use it in manual modes

due to limited flash space.

A buffer size of the gps drivers got reduced by 100 bytes.