arm: Add __aeabi_memclr in eabi_compat

LLVM's code generator will sometimes emit calls to __aeabi_memclr. Add an
implementation of this for LLVM compatibility.

Signed-off-by: Sam Edwards <CFSworks@gmail.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

arch/arm/lib/eabi_compat.c

@@ -37,3 +37,8 @@ void __aeabi_memset(void *dest, size_t n, int c)
 {
 	(void) memset(dest, c, n);
 }
+
+void __aeabi_memclr(void *dest, size_t n)
+{
+	(void) memset(dest, 0, n);
+}