intelmetool: Use correct type for pointer

Use `uintptr_t` instead of `uint32_t`, fixing the error below on 64-bit
systems, where pointers are 64-bit wide.

```
cc -O0 -g -Wall -W -Wno-unused-parameter -Wno-unused-but-set-variable -Wno-sign-compare -Wno-unused-function   -c -o intelmetool.o intelmetool.c
intelmetool.c: In function ‘dump_me_memory’:
intelmetool.c:85:45: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  dump = map_physical_exact((off_t)me_clone, (void *)me_clone, 0x2000000);
                                             ^
```

BUG=https://ticket.coreboot.org/issues/111
Change-Id: Id8d778e97090668ad9308a82b44c6b2b599fd6c3
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/19567
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
Reviewed-by: Paul Wise (Debian) <pabs@debian.org>

util/intelmetool/intelmetool.c

@@ -79,7 +79,7 @@ static void rehide_me() {
  * so we avoid cloning to this part.
  */
 static void dump_me_memory() {
-	uint32_t me_clone = 0x60000000;
+	uintptr_t me_clone = 0x60000000;
 	uint8_t *dump;
 
 	dump = map_physical_exact((off_t)me_clone, (void *)me_clone, 0x2000000);