LinuxKPI: Switch irq_work implementation back to standard taskqueue

from fast one as dmabuf does not run callbacks from critical sections
since drm-kmod 5.7.
Consumers which requires fair irq_work like drm-kmod 5.4 must #define
LKPI_IRQ_WORK_USE_FAST_TQ somewhere in source file before linux/irq_work.h
inclusion to enable old behavior.

MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D35052