lib/mpi: headers cleanup

lib/mpi: headers cleanup

MPI headers contain definitions for huge number of non-existing
functions.

Most part of these functions was removed in 2012 by Dmitry Kasatkin
 - 7cf4206a99d1 ("Remove unused code from MPI library")
 - 9e235dcaf4f6 ("Revert "crypto: GnuPG based MPI lib - additional ...")
 - bc95eeadf5c6 ("lib/mpi: removed unused functions")
however headers wwere not updated properly.

Also I deleted some unused macros.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Vasily Averin <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Dmitry Kasatkin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>