[FIX] layout/Splitter: Correct resizing keys
[FIX] layout/Splitter: Correct resizing keys

According to ACC spec the size of the first splitter area should be 
decreased when pressing up key.

Change-Id: Ia00e077966b5d0a306c09585d0925e22566851f9

SAP/openui5,olirogers/openui5,nzamani/openui5,olirogers/openui5,SQCLabs/openui5,olirogers/openui5,SAP/openui5,cschuff/openui5,SQCLabs/openui5,cschuff/openui5,cschuff/openui5,SQCLabs/openui5,nzamani/openui5,nzamani/openui5,SAP/openui5,SAP/openui5