ANDROID: sched: Remove duplicate const specifier

Fixes the following warning while building with GCC 7.3.0:

../kernel/sched/sched.h:1127:34: warning: duplicate ‘const’ declaration
specifier [-Wduplicate-decl-specifier]
  const struct sched_group_energy const *sge;
                                  ^~~~~

Change-Id: I779a2c042caa6e140cbcfe009070db57c9652970
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>