hostfs: fix a not needed double check

With the commit 3be2be0a we removed vmtruncate,
but actaully there is no need to call inode_newsize_ok() because the checks are
already done in inode_change_ok() at the begin of the function.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>