boot: android: free newbootargs when done

Free newbootargs when the concatenation is done and bootargs env
is set.

Fixes: 86f4695b ("image: Fix Android boot image support")
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Nicolas Belin <nbelin@baylibre.com>
Link: https://lore.kernel.org/r/20241217-fix-bootargs-concatenation-v2-2-b2fd7cf4e130@baylibre.com


Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>