SUNRPC: Remove xdr_buf_trim()

SUNRPC: Remove xdr_buf_trim()

The key action of xdr_buf_trim() is that it shortens buf->len, the
length of the xdr_buf's content. The other actions -- shortening the
head, pages, and tail components -- are actually not necessary. In
particular, changing the size of those components can corrupt the
RPC message contained in the buffer. This is an accident waiting to
happen rather than a current bug, as far as we know.

Signed-off-by: Chuck Lever <[email protected]>
Acked-by: Bruce Fields <[email protected]>
Signed-off-by: Anna Schumaker <[email protected]>