Revert part of "GPS: Don't set XTRA download pending flag at boot time."

libloc_api starts a thread as soon as the GPS is initialized, at
which time the xtra callback is also cleared.  If libloc_api gets
a request for xtra data from the gps before the xtra callback has
been set, it gets silently ignored, and never requests the data
again.  Since there is no method to see if data has been requested
in the interface, we must assume that data has been requested.

This would be better fixed in libloc_api by queuing the request
until gps-xtra is initialized, but libloc_api is still proprietary
for current devices.

This reverts part of commit 88606634.

The typo fix was not reverted.

Change-Id: I99a50dd64ff588d379dafb2974dd8d6b9229b6c6