[media] dib0700: Drop useless check when remote key is pressed

struct dvb_usb_device *d can never be NULL so don't waste time
checking for this.

Rationale: the urb's context is set when usb_fill_bulk_urb() is called
in dib0700_rc_setup(), and never changes after that. d is dereferenced
unconditionally in dib0700_rc_setup() so it can't be NULL or the
driver would crash right away.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>