media: dvb_ca_en50221: Fixed style issues on the whole file

- Running "checkpatch.pl -strict -f ..." gave more checks to fix.
  * Blank lines aren't necessary after an open brace '{'
  * Comparison to NULL written as "!<var>"
  * CHECK: Blank lines aren't necessary before a close brace '}'

Signed-off-by: Jasmin Jessich <jasmin@anw.at>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>