USB-serial fixes for v4.19-rc3

Here are two fixes for array-underflow bugs in completion handlers due
 to insufficient sanity checks.
 
 All have been in linux-next with no reported issues.
 
 Signed-off-by: Johan Hovold <johan@kernel.org>
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Merge tag 'usb-serial-4.19-rc3' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial into usb-linus

Johan writes:

USB-serial fixes for v4.19-rc3

Here are two fixes for array-underflow bugs in completion handlers due
to insufficient sanity checks.

All have been in linux-next with no reported issues.

Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/io_ti.h

@@ -173,7 +173,7 @@ struct ump_interrupt {
 }  __attribute__((packed));
 
 
-#define TIUMP_GET_PORT_FROM_CODE(c)	(((c) >> 4) - 3)
+#define TIUMP_GET_PORT_FROM_CODE(c)	(((c) >> 6) & 0x01)
 #define TIUMP_GET_FUNC_FROM_CODE(c)	((c) & 0x0f)
 #define TIUMP_INTERRUPT_CODE_LSR	0x03
 #define TIUMP_INTERRUPT_CODE_MSR	0x04

drivers/usb/serial/ti_usb_3410_5052.c

@@ -1119,7 +1119,7 @@ static void ti_break(struct tty_struct *tty, int break_state)
 
 static int ti_get_port_from_code(unsigned char code)
 {
-	return (code >> 4) - 3;
+	return (code >> 6) & 0x01;
 }
 
 static int ti_get_func_from_code(unsigned char code)