configs: meson64_android: use logo part label instead of index

To display the bootup logo, we read the gpt and assume that the
partition with index "2" will be the "logo" partition.

This might not always be the case, and it's very error-prone.

Load the logo partition by label instead of by index.

Signed-off-by: Guillaume La Roque <mkorpershoek@baylibre.com>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>