test: sctest: fix warnings

Perhaps we wanted to print these variables? Anyway, just make them
global, so the warnings will go away:

  gcc -o sctest.o sctest.c -Wall -g -O3 -I.. -I../include -L.. -lmodel
  sctest.c: In function ‘b’:
  sctest.c:20:6: warning: unused variable ‘r1’ [-Wunused-variable]
  sctest.c: In function ‘c’:
  sctest.c:26:6: warning: unused variable ‘r2’ [-Wunused-variable]
  sctest.c: In function ‘d’:
  sctest.c:33:6: warning: unused variable ‘r3’ [-Wunused-variable]