umcs(4) out-of-bound read

[Martin Pieuchot]

If the given `rate' is bigger than the last element of the array there's
an out-of-bound read and `divisor' will contain garbage.

Diff below fix this issue reported by coverity, CID 1453258.

Ok?

Index: umcs.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/umcs.c,v
retrieving revision 1.6
diff -u -p -r1.6 umcs.c
--- umcs.c      9 Oct 2017 08:26:16 -0000       1.6
+++ umcs.c      16 Mar 2020 18:56:28 -0000
@@ -451,16 +451,16 @@ umcs_calc_baudrate(uint32_t rate, uint16
                return (-1);
 
        for (i = 0; i < divisors_len - 1; i++) {
-            if (rate > umcs_baudrate_divisors[i] &&
-                rate <= umcs_baudrate_divisors[i + 1])
-                    break;
+               if (rate > umcs_baudrate_divisors[i] &&
+                   rate <= umcs_baudrate_divisors[i + 1]) {
+                       *divisor = umcs_baudrate_divisors[i + 1] / rate;
+                       /* 0x00 .. 0x70 */
+                       *clk = i << UMCS_SPx_CLK_SHIFT;
+                       return (0);
+               }
        }
 
-       *divisor = umcs_baudrate_divisors[i + 1] / rate;
-       /* 0x00 .. 0x70 */
-       *clk = i << UMCS_SPx_CLK_SHIFT;
-
-       return (0);
+       return (-1);
 }
 
 int