libpayload: In the USBMSC read_capacity function, make buf an array of u32.

That way when it's treated as a u32 when its value is extracted for numblocks
and blocksize below, it doesn't make the compiler unhappy, and it ensures that
the buffer will be properly aligned on architectures where that sort of thing
matters.

Built and saw warnings about type punning go away.

Change-Id: I254e0b5e70847112d660675b7df0ac9cb52e4051
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: http://review.coreboot.org/2653
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/payloads/libpayload/drivers/usb/usbmsc.c b/payloads/libpayload/drivers/usb/usbmsc.c
index 0032f58..16af448 100644
--- a/payloads/libpayload/drivers/usb/usbmsc.c
+++ b/payloads/libpayload/drivers/usb/usbmsc.c
@@ -375,14 +375,14 @@
 	cmdblock_t cb;
 	memset (&cb, 0, sizeof (cb));
 	cb.command = 0x25;	// read capacity
-	u8 buf[8];
+	u32 buf[2];
 
 	usb_debug ("Reading capacity of mass storage device.\n");
 	int count = 0, ret;
 	while (count++ < 20) {
 		switch (ret = execute_command
 				(dev, cbw_direction_data_in, (u8 *) &cb,
-				 sizeof (cb), buf, 8, 0)) {
+				 sizeof (cb), (u8 *)buf, 8, 0)) {
 		case MSC_COMMAND_OK:
 			break;
 		case MSC_COMMAND_FAIL:
@@ -398,8 +398,8 @@
 		MSC_INST (dev)->numblocks = 0xffffffff;
 		MSC_INST (dev)->blocksize = 512;
 	} else {
-		MSC_INST (dev)->numblocks = ntohl (*(u32 *) buf) + 1;
-		MSC_INST (dev)->blocksize = ntohl (*(u32 *) (buf + 4));
+		MSC_INST (dev)->numblocks = ntohl(buf[0]) + 1;
+		MSC_INST (dev)->blocksize = ntohl(buf[1]);
 	}
 	usb_debug ("  %d %d-byte sectors (%d MB)\n", MSC_INST (dev)->numblocks,
 		MSC_INST (dev)->blocksize,