mips: cacheinfo: Remove unnecessary increment of level

kernel test robot throws below warning ->

arch/mips/kernel/cacheinfo.c:112:3: warning: Variable 'level' is
modified but its new value is never used. [unreadVariable]

Remove unnecessary increment of level at the end.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>