rsi: move init_done flag to end of rsi_91x_init().

common->init_done flag should set after basic initialization. Hence,
moving init_done flag at end of rsi_91x_init().

Signed-off-by: Amol Hanwate <amol.hanwate@redpinesignals.com>
Signed-off-by: Siva Rebbagondla <siva.rebbagondla@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>