Added parameter <to_tag> to tools/check_changes.sh

Before this commit, only the changes in a branch from a tag to the HEAD
were generated. This commit enables listing the changes in a branch from
a tag to another tag or the HEAD of the branch.

Change-Id: I389a7a06b68dc727910afd417e6a74e4d620deab
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>