[media] media: em28xx - add error handling for KWORLD dvb_attach failures

Add error hanlding when EM2870_BOARD_KWORLD_A340 dvb_attach()
for fe and tuner fail in em28xx_dvb_init().

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>