fs/qnx4: decrement sizeof size in strncmp

As an identical match is wanted in this case, strcmp can be used instead.

The semantic match that lead to detecting this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression foo;
constant char *abc;
@@

*strncmp(foo, abc, sizeof(abc))
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Anders Larsen <al@alarsen.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>