staging: lustre: llite: basic port to xattr_handler API

Port the xattr functionality to the new xattr_handler API.
This is smallest changes needed to move to this new API. The
function ll_removexattr can be replaced by generic_removexattr
as well since it also uses the xattr_handler set xattr backend.
To tell the difference between the two cases we test the flag
passed in for XATTR_REPLACE. The ll_getxattr function is
replaced by the generic_getxattr function.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>