V4L/DVB (7093): radio-sf16fmi: fix request_region()

isapnp_fmi_probe attaches device. However, if request_region() fails, the
device isn't disattached.

Reviewed-by: Douglas Schilling Landgraf <dougsland@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>