[media] em28xx: don't break long lines

[media] em28xx: don't break long lines

Due to the 80-cols checkpatch warnings, several strings
were broken into multiple lines. This is not considered
a good practice anymore, as it makes harder to grep for
strings at the source code. So, join those continuation
lines.

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