drivers/intel/fsp2_0: Check for NULL before using pointer

The cbmem routines pass back NULL on error.  Check for this before using
the pointer.

Addresses coverity issue 1365731 - Dereference null return value

Change-Id: I92995366ffb15afd0950b9a8bbb6fe16252b2c38
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/17480
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/drivers/intel/fsp2_0/hand_off_block.c

@@ -106,6 +106,8 @@ static void save_hob_list(int is_recovery)
 {
 	uint32_t *cbmem_loc;
 	cbmem_loc = cbmem_add(CBMEM_ID_FSP_RUNTIME, sizeof(*cbmem_loc));
+	if (cbmem_loc == NULL)
+		die("Error: Could not add cbmem area for hob list.\n");
 	*cbmem_loc = (uintptr_t)fsp_get_hob_list();
 }