Fix undeclared deps on CTR_DRBG in programs/fuzz

While at it, fix a few other obvious ones such as ENTROPY and TIMING_C when
applicable.

A non-regression test for CTR_DRBG will be added in a follow-up commit.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/programs/fuzz/common.c b/programs/fuzz/common.c
index 5e6c84c..ac39ee2 100644
--- a/programs/fuzz/common.c
+++ b/programs/fuzz/common.c
@@ -58,8 +58,13 @@
     int ret;
     size_t i;
 
+#if defined(MBEDTLS_CTR_DRBG_C)
     //use mbedtls_ctr_drbg_random to find bugs in it
     ret = mbedtls_ctr_drbg_random(p_rng, output, output_len);
+#else
+    (void) p_rng;
+    ret = 0;
+#endif
     for (i=0; i<output_len; i++) {
         //replace result with pseudo random
         output[i] = (unsigned char) rand();