media: dvb_ca_en50221: Removed unused symbol

- The STATUSREG_TXERR definition is not used and it has style
  problems, too.  Removing it seems to solve both issues.

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