Differently from other Aspeed drivers, this driver calls clock
control APIs in interrupt context. Since ECLK is coupled with a
reset bit in clk-aspeed module, aspeed_clk_enable will make 10ms of
busy waiting delay for triggering the reset and it will eventually
disturb other drivers' interrupt handling. To fix this issue, this
commit changes this driver's irq to threaded irq so that the delay
can be happened in a thread context.

Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>