V4L/DVB (13856): ir-keytable: simplify and avoid a warning

/home/v4l/buildtest/v4l-dvb-master/v4l/ir-keytable.c: In function 'ir_setkeycode':
/home/v4l/buildtest/v4l-dvb-master/v4l/ir-keytable.c:190: warning: 'newkeymap' may be used uninitialized in this function

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