Eliminate top ground flood under GPS chip

Eliminate top ground flood under GPS chip

The top ground flood is useful under the RF section where we're trying
to dissapate heat from the PA; elsewhere, it's just
annoying. Eliminate it from under the GPS chip and get rid of a pile
of vias that might cause problems with the pads on the bottom of that chip.

Signed-off-by: Keith Packard <keithp@keithp.com>