egl/android: tweak droid_add_configs_for_visuals()

egl/android: tweak droid_add_configs_for_visuals()

Iterate over the driver_configs first in order to cut down the number of
getConfigAttrib() calls by a factor of 5.

While we're here, also drop the sentinel of the visuals array. We
already know its size so we can use that and save a few bytes.

v2: Use correct comparison in loop conditional (Eric)
    Use valid C initializer (Gurchetan)

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>