intelmetool: handle failures to mmap MEI memory

Fixes crashes when there is an error mapping memory.

    Error mapping physical memory 0x0000004275159040 [0x4000] ERRNO=1
    Segmentation fault (core dumped)

Change-Id: I5becc0c2870dd97297c4e8d1b101b95b31792ca7
Signed-off-by: Paul Wise <pabs3@bonedaddy.net>
Reviewed-on: https://review.coreboot.org/19562
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

util/intelmetool/intelmetool.c

@@ -83,6 +83,10 @@ static void dump_me_memory() {
 	uint8_t *dump;
 
 	dump = map_physical_exact((off_t)me_clone, (void *)me_clone, 0x2000000);
+	if (dump == NULL) {
+		printf("Could not map ME memory\n");
+		return;
+	}
 	zeroit(dump, 0x2000000);
 	printf("Send magic command for memory clone\n");
 
@@ -210,6 +214,12 @@ static int activate_me() {
 
 	rcba_phys = pci_read_long(sb, 0xf0) & 0xfffffffe;
 	rcba = map_physical((off_t)rcba_phys, size);
+	if (rcba == NULL) {
+		printf("Could not map MEI PCI device memory\n");
+		pci_free_dev(sb);
+		pci_cleanup(pacc);
+		return 1;
+	}
 
 	//printf("RCBA at 0x%08" PRIx32 "\n", (uint32_t)rcba_phys);
 	fd2 = *(uint32_t *)(rcba + FD2);