refactor(libc): clean up dependencies in libc

- Removing platform dependencies from libc modules.
- Replacing panicking with actual error handling.
- Debug macros are included indirectly from assert.h. Removing
  "platform_def.h" from assert.h and adding "common/debug.h"
  where the macros are used.
- Removing hack for fixing PLAT_LOG_LEVEL_ASSERT to 40.
  Instead removing assert with expression, as this
  does not provide additional information.

Signed-off-by: Claus Pedersen <claustbp@google.com>
Change-Id: Icc201ea7b63c1277e423c1cfd13fd6816c2bc568
diff --git a/drivers/measured_boot/rss/rss_measured_boot.c b/drivers/measured_boot/rss/rss_measured_boot.c
index fe2baf0..6cbb4dc 100644
--- a/drivers/measured_boot/rss/rss_measured_boot.c
+++ b/drivers/measured_boot/rss/rss_measured_boot.c
@@ -5,6 +5,7 @@
  */
 #include <assert.h>
 #include <stdint.h>
+#include <string.h>
 
 #include <common/debug.h>
 #include <drivers/auth/crypto_mod.h>