staging/easycap: style changes in easycap_low.c

remove uneedet brackets in ifs and switches
drop pointless castings
other small fixes

Cc: Mike Thomas <rmthomas@sciolus.org>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>