wil6210: check error in wil_target_reset()

When resetting target in wil_target_reset(), error may occur.
Indicate error via error code. In case of error, don't attempt to further
interact with card, specifically don't attempt firmware download or
interrupts enabling.

Move wil_rx_fini() to be always executed to prevent memory leak.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>