[SCSI] mpt2sas: move even handling of MPT2SAS_TURN_ON_FAULT_LED into process context

Driver was a sending a SEP request during interrupt context which
required to go to sleep.

The fix is to rearrange the code so a fake event
MPT2SAS_TURN_ON_FAULT_LED is fired from interrupt context, then later
during the kernel worker threads processing, the SEP request is issued
to firmware.

Cc: stable@kernel.org
Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <jbottomley@parallels.com>