USB: make transfer_buffer_lengths in struct urb field u32

Roel Kluin pointed out that transfer_buffer_lengths in struct urb was
declared as an 'int'.  This patch changes this field to be 'u32' to
prevent any potential negative conversion and comparison errors.

This triggered a few compiler warning messages when these fields were
being used with the min macro, so they have also been fixed up in this
patch.

Cc: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/misc/ftdi-elan.c b/drivers/usb/misc/ftdi-elan.c
index 79a7668..9d0675e 100644
--- a/drivers/usb/misc/ftdi-elan.c
+++ b/drivers/usb/misc/ftdi-elan.c
@@ -1568,7 +1568,7 @@
                         struct u132_target *target = &ftdi->target[ed];
                         struct u132_command *command = &ftdi->command[
                                 COMMAND_MASK & ftdi->command_next];
-                        int remaining_length = urb->transfer_buffer_length -
+                        u32 remaining_length = urb->transfer_buffer_length -
                                 urb->actual_length;
                         command->header = 0x82 | (ed << 5);
                         if (remaining_length == 0) {
@@ -1702,7 +1702,7 @@
                                 | (address << 0);
                         command->width = usb_maxpacket(urb->dev, urb->pipe,
                                 usb_pipeout(urb->pipe));
-                        command->follows = min(1024,
+                        command->follows = min_t(u32, 1024,
                                 urb->transfer_buffer_length -
                                 urb->actual_length);
                         command->value = 0;
@@ -1766,7 +1766,7 @@
                 mutex_lock(&ftdi->u132_lock);
                 command_size = ftdi->command_next - ftdi->command_head;
                 if (command_size < COMMAND_SIZE) {
-                        int remaining_length = urb->transfer_buffer_length -
+                        u32 remaining_length = urb->transfer_buffer_length -
                                 urb->actual_length;
                         struct u132_target *target = &ftdi->target[ed];
                         struct u132_command *command = &ftdi->command[