mfd: ezx-pcap: Avoid rescheduling after destroying workqueue

Driver allocates workqueue and then registers additional interrupt
handler with devm interface. This means that device removal will not
use a reversed order, but first destroy workqueue and then, via devm
release handlers, free the interrupt.

The interrupt handler registered with devm does not directly
use/schedule work items on the workqueue and the remove() function
correctly removes other IRQs handlers, however the code mixing devm and
non-devm interfaces is difficult to analyze and read.

Make the code flow much more obvious by using devm interface for
allocating the workqueue, so it will be freed with the rest of devm
resources.

Change is not equivalent in the workqueue itself: use non-legacy API
which does not set (__WQ_LEGACY | WQ_MEM_RECLAIM). The workqueue is
used to update device registers, thus there is no point to run it for
memory reclaim.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260305-workqueue-devm-v2-9-66a38741c652@oss.qualcomm.com
Signed-off-by: Lee Jones <lee@kernel.org>