[media] media/rc/imon.c: avoid flooding syslog with "unknown keypress" when keypad is pressed

My 15c2:0036 device floods syslog when a keypad key is pressed:

	Feb 18 19:00:57 homeserver kernel: imon 5-1:1.0: imon_incoming_packet: unknown keypress, code 0x100fff2
	Feb 18 19:00:57 homeserver kernel: imon 5-1:1.0: imon_incoming_packet: unknown keypress, code 0x100fef2
	Feb 18 19:00:57 homeserver kernel: imon 5-1:1.0: imon_incoming_packet: unknown keypress, code 0x100fff2
	Feb 18 19:00:57 homeserver kernel: imon 5-1:1.0: imon_incoming_packet: unknown keypress, code 0x100fff2
	Feb 18 19:00:57 homeserver kernel: imon 5-1:1.0: imon_incoming_packet: unknown keypress, code 0x100fff2

This patch removes those messages from imon, following suggestion from
Mauro. Unknown keys shall be correctly handled by rc/input layer.

Signed-off-by: Kevin Baradon <kevin.baradon@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>