media: img-ir-hw: fix one kernel-doc comment

Needed to suppress the following warnings:
	drivers/media/rc/img-ir/img-ir-hw.c:351: warning: No description found for parameter 'reg_timings'
	drivers/media/rc/img-ir/img-ir-hw.c:351: warning: Excess function parameter 'timings' description in 'img_ir_decoder_convert'

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>