iio: dummy_evgen: remove Excess kernel-doc comments

Drop kernel-doc comments for struct fields that were removed to
prevent kernel-doc warnings:

iio_dummy_evgen.c:43: warning: Excess struct member 'irq_sim' description in 'iio_dummy_eventgen'
iio_dummy_evgen.c:43: warning: Excess struct member 'base' description in 'iio_dummy_eventgen'

Fixes: 337cbeb2c13e ("genirq/irq_sim: Simplify the API")
Signed-off-by: Randy Dunlap <[e-mail]>
Reviewed-by: Bartosz Golaszewski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/dummy/iio_dummy_evgen.c

···
  * @regs: irq regs we are faking
  * @lock: protect the evgen state
  * @inuse: mask of which irqs are connected
- * @irq_sim: interrupt simulator
- * @base: base of irq range
  * @irq_sim_domain: irq simulator domain
  */
 struct iio_dummy_eventgen {