[media] rc: img-ir: hw: Fix min/max bits setup

The calculated values for the minlen and maxlen fields, which were
rounded to multiples of 2 and clamped to a valid range, were left
unused. Use them in the calculation of the register value rather than
using the raw input minlen and maxlen.

This fixes the following warning with a W=1 build:
drivers/media/rc/img-ir/img-ir-hw.c In function ‘img_ir_free_timing’:
drivers/media/rc/img-ir/img-ir-hw.c +228 :23: warning: variable ‘maxlen’ set but not used [-Wunused-but-set-variable]
drivers/media/rc/img-ir/img-ir-hw.c +228 :15: warning: variable ‘minlen’ set but not used [-Wunused-but-set-variable]

Reported-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>