[media] em28xx: Fix: I2C_CLK write error message checks wrong return code

It looks like the return value check that is done after setting the I2C
speed checks the wrong return code.

Signed-off-by: Sascha Sommer <saschasommer@freenet.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>