minix: remove !NO_TRUNCATE code

This patch removes the !NO_TRUNCATE code that anyway required a manual
editing of the code for being used.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>