fs: yaffs2: switch to the new prototype for ->set/getxattr()

Since commit 3767e255 ("switch ->setxattr() to passing dentry and
inode separately") and commit ce23e640 ("->getxattr(): pass dentry
and inode as separate arguments"), a new inode argument has been added
for these two functions. Adjust these two functions to accommodate to
this change.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>