lsi: Fix value overflow in request tag processing

This fixes a mismerge of 64d564094cac5f72eeaeb950c442b773a00d3586 (wrong
patch version): We need to mask the tag value properly to obtain its
device ID.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
