media: ir-nec-decoder: fix kernel-doc parameters

Some parameters aren't correctly identified, as noticed by
those warnings:
	drivers/media/rc/ir-nec-decoder.c:49: warning: No description found for parameter 'ev'
	drivers/media/rc/ir-nec-decoder.c:49: warning: Excess function parameter 'duration' description in 'ir_nec_decode'
	drivers/media/rc/ir-nec-decoder.c:189: warning: Excess function parameter 'raw' description in 'ir_nec_scancode_to_raw'

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