staging: xillybus: fix some coding style errors

This includes:
 - keep "else" on the same line as the closing brace
 - don't use "else" after "return"
 - don't issue a message for an out-of-memory error
 - blank line after a declaration

Signed-off-by: Vincent Bernat <vincent@bernat.im>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>