perf tools: fix build for another rbtree.c change

perf tools: fix build for another rbtree.c change

Fixes:

../../lib/rbtree.c: In function 'rb_insert_color':
../../lib/rbtree.c:95:9: error: 'true' undeclared (first use in this function)
../../lib/rbtree.c:95:9: note: each undeclared identifier is reported only once for each function it appears in
../../lib/rbtree.c: In function '__rb_erase_color':
../../lib/rbtree.c:216:9: error: 'true' undeclared (first use in this function)
../../lib/rbtree.c: In function 'rb_erase':
../../lib/rbtree.c:368:2: error: unknown type name 'bool'
make: *** [util/rbtree.o] Error 1

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Michel Lespinasse <walken@google.com>
Reported-by: Alexander Shishkin <alexander.shishkin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>