kdrive: fix build error on gcc 4.8 for out-of-bounds array access

I'm getting a error building xorg-server-1.14.1.902 with thelatest snapshot
of gcc-4.8:

input.c:225:43: error: array subscript is above array bounds
[-Werror=array-bounds]

This is because kdNumInputFds can become equal to KD_MAX_INPUT_FDS in
KdRegisterFd(). This means that in KdUnregisterFd(), kdInputFds[j + 1] can
be beyond the end of the array.

Signed-off-by: Chris Clayton <chris2553@googlemail.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

hw/kdrive/src/kinput.c

@@ -221,7 +221,7 @@ KdUnregisterFd(void *closure, int fd, Bool do_close)
             if (do_close)
                 close(kdInputFds[i].fd);
             kdNumInputFds--;
-            for (j = i; j < kdNumInputFds; j++)
+            for (j = i; j < (kdNumInputFds - 1); j++)
                 kdInputFds[j] = kdInputFds[j + 1];
             break;
         }