lib/mpi/mpi-bit.c: fix spello of "functions"

Fix typo/spello of "functions".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/8df15173-a6df-9426-7cad-a2d279bf1170@infradead.org


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>