kernel/main: get rid of unused variable warning
kernel/main: get rid of unused variable warning

RWTH-OS/HermitCore,stlankes/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,stlankes/HermitCore,RWTH-OS/HermitCore,RWTH-OS/HermitCore,stlankes/HermitCore,stlankes/HermitCore,stlankes/HermitCore,stlankes/HermitCore