media: em28xx-core: fix most coding style issues

There are a number of coding style issues at em28xx-core.
Fix most of them, by using checkpatch in strict mode to point
for it.

Automatic fixes were made with --fix-inplace, but those
were complemented by manual work.

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