hv:fix "missing for discarded return value" for memset

No need to check the return value for memset
code like this:
int a(void) {
	return 0;
}
int b(void){
	a();
}
fix as follow:
int a(void) {
	return 0;
}
int b(void){
	(void)a();
}

Signed-off-by: Mingqiang Chi <mingqiang.chi@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/lib/memory.c

@@ -272,7 +272,7 @@ void *calloc(unsigned int num_elements, unsigned int element_size)
         /* Determine if memory was allocated */
         if (memory != NULL) {
                 /* Zero all the memory */
-                memset(memory, 0, num_elements * element_size);
+		(void)memset(memory, 0, num_elements * element_size);
         }
 
         /* Return pointer to memory */