benchmarks: eine: include header for using time()

../src/benchmarks/eina/eina_bench_sort.c: In function ‘eina_bench_sort_eina’:
../src/benchmarks/eina/eina_bench_sort.c:52:10: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
    srand(time(NULL));

Found due to the nice quite build output in our meson feature branch.

src/benchmarks/eina/eina_bench_sort.c

@@ -22,6 +22,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 
 #ifdef EINA_BENCH_HAVE_GLIB
 # include <glib.h>