libefi: pdinfo_t pd_unit and pd_open should be unsigned

The device index, partition index and reference counter are all positive
numbers. However, since our internal partition number may be negative
to indicate GPT table, the compare expression need to take care when comparing
pdinfo_t and partition data.

sys/boot/efi/include/efilib.h

@@ -56,8 +56,8 @@ typedef struct pdinfo
 	EFI_HANDLE		pd_alias;
 	EFI_DEVICE_PATH		*pd_devpath;
 	EFI_BLOCK_IO		*pd_blkio;
-	int			pd_unit;	/* unit number */
-	int			pd_open;	/* reference counter */
+	uint32_t		pd_unit;	/* unit number */
+	uint32_t		pd_open;	/* reference counter */
 	void			*pd_bcache;	/* buffer cache data */
 } pdinfo_t;
 

sys/boot/efi/loader/main.c

@@ -901,7 +901,7 @@ command_chain(int argc, char *argv[])
 				/*
 				 * d_partition should be 255
 				 */
-				if (pd->pd_unit == d_dev->d_slice) {
+				if (pd->pd_unit == (uint32_t)d_dev->d_slice) {
 					loaded_image->DeviceHandle =
 					    pd->pd_handle;
 					break;