nvme_disk: Add missing cast to off_t.

Should fix the 64-bit build.

src/add-ons/kernel/drivers/disk/nvme/nvme_disk.cpp

@@ -424,7 +424,7 @@ nvme_disk_read(void* cookie, off_t pos, void* buffer, size_t* length)
 			// The "rounded_len" will be the actual transferred length, but
 			// of course it will contain the padding.
 			*length = std::min(*length, (size_t)std::max((off_t)0,
-				rounded_len - (off_t)(pos - rounded_pos)));
+				(off_t)rounded_len - (off_t)(pos - rounded_pos)));
 			if (*length == 0)
 				return status;
 		}
@@ -499,7 +499,7 @@ nvme_disk_write(void* cookie, off_t pos, const void* buffer, size_t* length)
 			&rounded_len, true);
 		if (status != B_OK) {
 			*length = std::min(*length, (size_t)std::max((off_t)0,
-				rounded_len - (off_t)(pos - rounded_pos)));
+				(off_t)rounded_len - (off_t)(pos - rounded_pos)));
 		}
 		return status;
 	}