Staging: dt3155: fix coding style issues in dt3155_io.c

This fixes up the sparse and coding style issues found in the
dt3155_io.c file.

No code is changed, only formatting and removing unused code.

Cc: Scott Smedley <ss@aao.gov.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>