scripts/sysgen: Fix indentation inconsistency

scripts/kconfig/conf --silentoldconfig Kconfig
  Using /home/<user>/zephyr.git as source for kernel
  GEN     ./Makefile
  CHK     include/generated/version.h
  UPD     include/generated/version.h
  HOSTCC  scripts/gen_idt/gen_idt.o
  HOSTLD  scripts/gen_idt/gen_idt
  CHK     misc/generated/configs.c
  UPD     misc/generated/configs.c
  CHK     include/generated/offsets.h
  UPD     include/generated/offsets.h
  CHK     misc/generated/sysgen/prj.mdef
  UPD     misc/generated/sysgen/prj.mdef
  File "/home/<user>/zephyr.git/scripts/sysgen", line 461
    kernel_main_c_out("extern int %s(int event);\n"% (event[1]))
                                                               ^
TabError: inconsistent use of tabs and spaces in indentation
/home/<user>/zephyr.git/./Kbuild:51: recipe for target 'misc/generated/sysgen/kernel_main.c' failed
make[3]: *** [misc/generated/sysgen/kernel_main.c] Error 1
/home/<user>/zephyr.git/Makefile:904: recipe for target 'prepare' failed
make[2]: *** [prepare] Error 2
make[2]: Leaving directory '/home/<user>/zephyr.git/tests/bluetooth/shell/outdir'
Makefile:169: recipe for target 'sub-make' failed
make[1]: *** [sub-make] Error 2
make[1]: Leaving directory '/home/<user>/zephyr.git'
/home/<user>/zephyr.git/Makefile.inc:63: recipe for target 'all' failed
make: *** [all] Error 2
make: Leaving directory '/home/<user>/zephyr.git/tests/bluetooth/shell'

Change-Id: Id6dbf7ef1c0b95a68cf4265465a0124c16e6f971
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>