net: airoha: fix error branch in airoha_dev_xmit and airoha_set_gdm_ports

Fix error case management in airoha_dev_xmit routine since we need to
DMA unmap pending buffers starting from q->head.
Moreover fix a typo in error case branch in airoha_set_gdm_ports
routine.

Fixes: 23020f04 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/b628871bc8ae4861b5e2ab4db90aaf373cbb7cee.1721203880.git.lorenzo@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>